Some good advice so far on here. Lets see if I can't screw that up
Where a lot of people make their mistakes is not forming an operating budget, a cost of doing business if you will. Cost to build a car is one thing and in a lot of cases is actually the cheapest part. The actual cost of racing and maintaining said vehicle is commonly overlooked and is the reason why most either stop racing or are flashes in the pan.
Items like fuel for car and tow vehicle, lodging, food, wear items like clutches/brakes/tires/oil, parts breakage, R&D, testing, entry fees, time away from family/work/business, parts refreshening and/or replacement. It's pretty easy to spend $6,000-$24,000(or beyond) in a year of racing not including buying the car/rig/trailor. Be sure to spend the money where it needs to be spent.
If a person is a car guy first then they should build a car that they actually like and are familiar with. Otherwise it's much easier to become disinterested and frustrated with the whole thing. It takes dedication to build a class specific car.
Don't become distracted from your own program by always worrying about what so and so is doing. Getting immersed in politics is a sure fire way to take you eye off the ball. And worse yet if a person hasn't made the commitment to build a car for a class do not start reading up on all the BS politics going on or that will discourage you.(instantly if you feel your getting the raw end, or over time because you get tired of hearing the whining).
Do not use debt as a tool for anything. Especially on racing and race cars. The monthly payments is what makes longterm harder and harder and also a makes it easier to overspend on items.
The more you can do on your own the cheaper it can be. (Be careful as your time is worth money also. 300-1,000 or how many ever hours at the shop are hours away from working or running the business on the financial side and away from family on the personal side) working on your own stuff has a certain amount of gratification to it also and can be a lot of fun and a bonding experience.
Make a plan. Write it down. On paper On purpose.
(Do not sacrifice your future or your families well being for anything. Take care of the household first and foremost.)
Last note: Some classes are perceived as "Entry level". And though this is true as being entry level to class specific racing. It is not entry level for a new drag racer. Entry level to the sport is the test and tunes and local bracket races. I wanted to go class racing after only a few Test and Tunes under my belt. Big mistake on my part as I learned quickly how much I didn't know(and some things I still don't know). The learning curve in class racing is steep. I started seeing everything that went on behind the scenes and you quickly gain a whole new respect for those people that are racing and have been racing for years. (And the 2nd thing that blows you away is the camaraderie in most people's cases)