This is how I do it
My job doesn't pay well, but I get a lot of opportunity to work overtime. A little over 2k so far this year, but I haven't worked a lot of OT relative to previous years.
I use my cc but pay it off at the end of the month. We'll all except the last three months. (flame2) Luckily, I got a pretty big bonus this month and a large reimbursement as well. . . .that'll help pay off the cc from the last three months. I also perform mods, maintenance, and repairs on other people's cars for spare cash. On Saturday, I have two people stopping buy. I'm also doing extensive stuff on another car -- his bill is 2k so far. He'll be on a payment plan. The cool thing is he's real active in car shows and is part of a number of car clubs. A lot of people I've met through him were real excited about the work I've done and the low cost.
I wouldn't recommend it, but you can do the same thing. Spend a little on tools, do your mods/maintenance/repairs yourself and learn from it. After that you can help others with their woes. Since I don't have the overhead that garages have, I can usually get a job done for 1/3-1/2 the price of what's charged at a shop -- people like that. They get a good deal, you get paid. There are risks though. Keep in mind, sometimes things don't go according to plan and the top priority is taking care of your customer. I've come out behind on certain people's vehicles, but they've come back with more than enough $ to make up for my loss.
Now if you come back and say, I don't have a garage to work in b/c I live in an apartment where they don't allow you to work on cars. FIX IT. . . move. If you plan on being in the same area for the next 5 or so years, buy a house --> build equity.
My P5 isn't really modified. Just an intake. Although, I was considering a turbo kit. Most of my modding has been done to my other car, and recently, I've started on my truck. I've spent about 9k in mods last year, but I'll have a low 12/high 11 FWD daily driver when I'm done.
I most always buy used, eBay, or discounted from a reseller via GB or just knowing the business owner. Avoid buying parts while there's a lot of hype. A few months after the hype dies down, people start selling parts off like mad. In the past few weeks, there was a FM turbo kit for 1900 as well as a HiBoost w/ injectors for 3500. That's when you want to move.
Before doing that, create a list of mods that you want. That way you only buy something off that list, not just every good deal that comes buy.