how to save money building your car

Great topic. I suppose if all of us were 'capable of' doing all (or most) of the work ourselves, that would help a great deal. However, knowledge is not inherited - it is developed, and IF we were all on the same level playing field, we'd basically all be in the same business. But, regretfully, our hobbies and interests often get delayed or derailed by real life's challenges and priorities. Some of the older members, with vast knowledge and experience, are either slowed by health issues - or - just not as eager and enthused as they were in the beginning.
But, having said this much, the affordable restos involve doing the 'leg-work' and little things - - that ultimately (and eventually) add to the total cost. Big things that pretty much have to be 'farmed-out' would be machine work, GOOD paint in paint booth, vinyl roof and custom upholstery and - - CHROME work.
I took my tech training 35 years ago and do my own engines and trannys. Some rear ends need specialty tools but steering and suspensions are totally do-able by you and me.
Wholesale parts are a no-brainer and stay away from expensive and needless 'upgrades'. Avoid (45 yr.old) NOS stuff - only to have genuine Mopar logo or PN on it. Case and point - - was searching on Ebay last night for replacement washer reservoir (for my Signet). I noticed one ad where gentleman has an OEM/NOS (yellowed and likely almost brittle with age) A-body tank for sale. His price? $500. (US) or - - $685. (CDN) !! Plus, another $65. shipping, etc. Who is going to buy this? I then search more and find better tank for (only) $49. US.
One more point is to never spend/invest (lol) more on a vehicle than you would hope to get out of it - - - IF you ever choose to sell it. And, if serial no. shows anything less than a 340, consider repairing and maintaining - instead of restoring.