Before you get started you need to do some research to decide what kind of car you want to build. Take some time and visit a few local Hot Rod, Custom, Classic, or Antique car shows. Start by doing a web search for “hot rod shows” Classic Car Shows in your neighborhood and I’m sure you will find a few shows within a short driving distance of your home. Visit some of these shows and notice all the different cars you will see that may help you make a project decision. Also it is very important to take a lot of pictures at these shows, because otherwise you will not remember everything you saw and some of these pictures will have some good details for you future project.
As you visit these shows ask a lot of questions about who built the cars, who painted the cars, who did the interior, who did the sound, who did the chrome, who polished the stainless, who did the chassis work, drive train, wiring; you may need to reference any of these folks in the future with your project. One key point to remember is that many of these shops are experts in their field but they have limited staffs that are focused on the service they provide as a result many of these "small shops" may not have a website.
Before you jump into your project feet first just be aware building a project car can be very expensive. However there are three other options to reduce your cost.
Find a project car that you would like where the owner has lost interest. Often times all the major work has been done and all the car needs is a drive train, paint and/or upholstery work. Just calculate the price of the car, drive train and paint and interior and you could come out way ahead financially.
Consider a motor and transmission from a recently dismantled late model car, it could save you a few dollars compared to a new or remanufactured/rebuilt set.
If cost is your main consideration, find a completely finished car that you really like and just buy it as is. This way you come out way ahead by avoiding all the labor cost of building a car. Then you can personalize the car with your own choice of wheels and tires, new paint, pen striping etc..
Many Hot Rods and Customs sell in a range from $30-$60 K and trust me the builder easily has put 50-100% more into the build of that car. Classics and Antiques can easily cost upwards of $75 K; have you ever watched the Barrett Jackson or Mecum Auto Auctions? These auctions usually deal with very high end cars especially Barrett Jackson. That being said I've seen a lot of very nice cars that have sold for as little a $25-$40 K. If you’re planning to do a frame off, strip the body down to the metal kind of project, make sure you take pictures throughout the process and save all your receipts. If you ever decide to sell the car the pictures and receipts could help you get a higher price for the car. Seldom ever will you get what you have invested, so make sure you pick a project that you can enjoy and drive for a few years. For me personally I have a file folder with a lot of receipts for my Buick that have never been totaled and I have no regrets. The fun and enjoyment we've had and the people we've met over the past 5 years has been worth every penny spent.