Lumber is tough these days - expensive, and poor quality. I used to be able to pull any #2 1x4 off the stack and it would be usable and the cost would be negligible. Now, I need to go up a couple of level$ in order to get straight boards and still need to choose carefully. Fortunately, lumber is a one-time purchase and there are many ways to mitigate the cost. Scour the neighborhood and watch for discards, dumpster dive at construction sites (ask, and be safe and legal!), watch for sales and stock up. Use substitutes for sheet goods - 3/4" plywood and baltic birch are often overkill - 3/8 or 1/2" is usually sufficient, and OSB roof decking is much less costly and plenty strong. I'm still re-using lumber from layouts that I built 40 years ago.
Regarding the trains themselves, postwar and MPC items are out of favor - there are lots of good running pieces that can be found at bargain prices. If a person wants more detail, MTH PS1 locos have a lot of detail and are hundreds of dollars cheaper than their PS2 and PS3 counterparts. Don't forget Williams - they're great runners with a reasonable level of detail, and lots of NOS are available. Sure, conventional engines don't have the latest bells and whistles, but you don't need to buy an expensive digital operating system.
It can be done...
