A discussion on tithing

I finally got caught. Yep the bishop finally got ahold of me to talk about why my donations are down. To tell you the truth I was a little relieved that I got called into his office. I could finally tell him my story of how and why I lost my testimony of tithing and I did. I told him how we struggled when we first moved to Utah. How I never asked for help when so many "struggling" families did. I asked questions such as how can a family who is paying on a half a million dollar house with two new cars in the driveway justify asking their bishop for help with food or a mortgage payment when the Husband loses his job. I also talked about my frustrations with the members accepting government assistance while attending college. Why do they get a pass on baby expenses and I don't. It was a good meeting unfortunately my testimony didn't grow as soon as I walked out the door. That will take some time but I truly hope it does. I miss having a strong testimony of tithing and blessings that come from that princable. I have had blessings from tithing but lately have the hardest time seeing them.
Anyways, I've started to pay tithing and it got me thinking. Is there such a thing as negative income or tithing exempt income? The church explanation of tithing is "To tithe is to give freely one/tenth of one's income annually to the church

or as I've heard it before 10% of your annual interest earned. Here's the question? What is that? Well my dad (who I recently found out had 2 of my brothers paid for on the government's dime) Says you should pay on your gross pay. "You have an obligation to pay taxes therefore your income is your gross income" he says. My wife disagrees. My wife says because you don't know how much you truly have to pay in taxes you should pay on net income. If you get a tax return then pay on your tax return. I think the answer lies a little deeper than that. Let me explain with a few scenarios.
Before I begin let me say this. This is not a petition for change. If you feel like you need to pay off your gross pay do it. If you feel like you need to pay off your net, do it. This is not an argument that we are doing it wrong Just a discussion with questions about doing it right.
First question or discussion for those who are gross payers. Within my paycheck I have pre tax items. Dental, vision, medical, 401k and hsa. After those have been deducted then I get taxed. They take out state federal and social security. The social security is future income. The faith is (even though everyone knows it's dying) you will have that someday as income. Because it's impossible to determine how much you will withdraw why are you paying tithing on it right now? Wouldn't it make more sense to pay for it later if you make it to retirement? Or if it's still around. The other deduction after gross pay is your 401k. Same questions why are you paying tithing on that right now. That is future income. It makes more sense to me when I withdraw retirement to pay tithing then. Unless you believe you won't have to pay it later. Both of those pay you more than what you paid plus who knows how much you will be able to withdraw vs what you paid.

Second scenario is my favorite argument so far. Say a person owns a painting buisness. On a particular day this person goes out to his driveway starts his personal/company van and heads to his job sight. On his way he puts gas in his van and buys painting supplies. When he's done with the job his employer/customer who hires him pays him 500 dollars for the job and the painter goes home.
Here's the question. What does he pay tithing on? He got paid 500 dollars so his 10% cut to the church is 50 dollars right?
No. His income is not based on what his customer/employer paid him. In order to get the job done he needed gas for his van and painting supplies. Both are required and included in his estimate. His bottom line. Income, and prophets are calculated after his expenses. It's from that he would declare his income and pay his tithing off of. That brings me to my argument. Should the gas you buy to go to work be includes as tithable income? The example above does not because he owns his own
business but consider these points. If in order to make money you need to spend money, wouldn't the money you spent be considered negative income? A painter needs painting supplies and gas to complete his job. Both negatively impact his bottom line. Gas or as I call it work gas used to go to and from work negatively impact my weeks pay thus I argue that gas from a REASONABLE good mileage car that is bought to "make money" would be a tithing exempt item. I say reasonable because I don't agree with this if it's abused. A person who purposely buys a deisel truck to work at a factory job should reconsider their stance on this argument. Their are so many less inexpensive choices that could be made but if that was your only vehicle you had plans to change it and you had no other choice I would agree that your fuel money should be tithing exempt.

My last and final argument and open Question is this. There are so many things we buy that we NEED that include interest. Unfortunately for most of us owning a house with no mortgage payment will be hard to accomplish. In order for most of us to own a place to live we have to pay a sizeable amount of interest to the mortgage company plus PMI plus taxes that negatively affect our income. If each and every house was interest and PMI free some of us would have an extra 600 dollars in our pocket every month but because we didn't inherit enough money to buy a house we need to take out loans to buy a place to live. We lose money every month on that BUISNESS  investment. Should that not be considered lost income? Taxes say it is. What about credit cards? I just put our hospital bill on a credit card in good faith that I would save money. Not only did I not save any money I probably will end up paying interest on that credit card. I lost money on my decision. Should that not be considered lost income. I could go on and on but will end with this last scenario. I know of at least one couple briefly mentioned in my first post who had their house paid off by their parents. Eventually they made the decision to move to new york to be closer to a specialist because their son has a medical condition which means they sold their house. They sold it for a reasonable prophet. So since they got it for free as a gift did they A. Put all the money including prophets into a bank account to pay for their new house claiming it was a gift and they don't need to pay tithing on a gift. B. Pay tithing on the prophets or C. Pay tithing on the entire house? I honestly don't know but it does bring up a few more questions. Technically it seems to me that a person can make an argument that they will pay tithing on a house after they sell it. They can say that it's an investment and that all payments toward the house are an investment for future interest or prophets. After the house is either paid off or sold then will tithing be paid. An investment  into a future paycheck.
 In closing my argument let me say this. I like how the church makes the rule of tithing vague. There's no rule that says you pay off gross or net pay. If that's what your comfortable with then pay that. I'm just bringing up some thoughts and opinions for an individual with unique circumstances. I have already  decided what is my positive income and what negative incomes affect my positive income creating a annual interest earned that I am comfortable declaring a full tithing paid.