I'm in my first year racing, and I've gotten a lot of great help and advice here on the board, and out on the track. All the answers that have been posted so far are right on. Change your "Preferences" here on the board (look in the upper right corner of the page) - you can view topics from the past year or more, and see what advice has already been given to newbies, and also see old discussions about prep (and problems) on the specific car models.

I bought a car that I thought was "ready" - and spent the season removing everything the former owner installed - things I had paid a premium to get. If I bought a "built" car again, it would only be one I had seen race, and only from a racer I trusted (either someone I know or someone known by people I respect). From my own rather painful experience - there is no such thing as saving money in racing. What looks like the cheaper way going in often ends up being the expensive way in the end. Particularly true with building a car - that's why they're saying it has to be a labor of love. Figure that every dollar you spend improving the car will add about 25 cents to its value - and only if you do it right (or find a sucker to buy it). Look twice before you leap - unless your goal is to hate racing so you can save your money for some other hobby. :-)

Consider renting a car your first year, so you can focus on driving skills instead of getting the bugs out of the car.

There are always cars for sale - don't worry about losing this or that deal. Find out what you're getting into first, then worry about getting the right deal. And consider volunteering before racing - it helps to know folks, and you learn a lot about racing, the other drivers, and the organization. I wouldn't have stuck it out this long without the help and encouragement of the workers and other drivers - I can't even imagine what a miserable year it would have been if, in addition to having my car break again and again, the workers had thought my tension and confusion were impatience and egotism. Talk to the other drivers at the track - they'll show you their setups, give you advice and encouragement, and welcome you into the fold. I can't speak for others, but if a newbie showed up offering to crew for me, I'd welcome him or her - and I'd certainly let them play with my car (I had a crew person, once, and she drove my car in a High Performance Driving Event - HPDE).

P.S. You didn't mention driving experience - you can run HPDEs and autocross in a street car, which is a cheaper way to get started while building car control skills that will help when you start racing.