What advice about that process would you give your past self 20 years before you built the house?
I wish you luck on this and I hope you see it through but a lot of things change in twenty years.
I have been inadvertently working on houses (mostly my own) for many years. I say "Inadvertently" because, in the beginning, I didn't want to but it was a necessity. I had a house in Sacramento that was built in 1949. We put new siding on it and sold it after 13 months for a 50% profit.
We then bought a new house that was still being built in a subdivision. We stayed in our old house and rented it from the new buyer for less than what our mortgage payment was previously. We rented for 9 months while the new house was being built.
I had the opportunity to go to the new house almost every night after work to see what had been done and what they had screwed up. I ended up having a good working relationship with the GC (who they called "The Foremen") and he turned a blind eye to me working on the house while it was being built (plus, our house was not visible from the foreman's temporary office trailer). This was a little risky for the builder because these houses (there were 6 being built and eventually many more) can fall out of escrow and then the builder would be stuck with whatever I had done.
I ran wiring for things I wanted to add later. I fixed HVAC ducts that were installed and then completely pinched closed by the next crew that came out (because they didn't care about someone else's work).
We lived in that house for 30 years and eventually rebuilt the kitchen and 3 bathrooms. We had the roof replaced, installed solar, replaced the HVAC, painted the exterior 3 times and replaced a big chuck of T-111 siding.
We sold that house for a tremendous 300% profit and bought a house on a lake in Alabama (as you know from other threads). We are rebuilding this house as we live in it. We have lived in a construction zone for so long, it would seem weird not to now. The kitchen is definitely the hardest room to have disabled because it is the center of activity.
I have friends who have/are building houses and have done it in many ways;
1) buy and old house and live in it while rebuilding.
2) I know a guy that had a slab poured and a steel building erected (Fast) and now he is building a structure inside of it to live in while he builds his dream house. The steel structure with the living quarters will eventually become a workshop with an apartment. But really, he could live in the apartment permanently if he never finishes the dream house.
As far as money, I don't know about new construction because there are many variables like, the utilities. If your property does not have electric, gas, water and septic/sewer, then these things are very expensive. I have a friend that bought a backhoe to dig his own utilities but he went bankrupt before finishing his dream house, then his wife left him...not a good story. When you rebuild an existing house, you already have utilities and a place to live while rebuilding (if you can work around the construction). It will cost around $150,000 to $250,000 to rebuild a house depending on what you want and how much you can do yourself. Personally, I wouldn't want to sub it out because people don't care as much about your house as you do.
When we bought our house, the kitchen was fully functional but ugly and had rot under the kitchen sink.
It helps if you can find some hottie to help you!
This was the worst phase because we had no sink for a while. Luckily, this house has a secondary kitchen.
I took a chunk of the old counter and put it on two Harbor Freight dollies and made a temporary rolling island. We used the kitchen all the way through the reno.
As far as saving for the future, I know Dave Ramsey would say to pay off your mortgage and bank your income until you become a millionaire! That never worked for me though, and I'm not even sure I trust banks right now. The banks won't tell you their real status until it's too late. Only the "Insiders", the deep state, what ever you call them know what's going on. The only way I've made big money is by selling real estate.