The second phase of the plan is to build an ADU.

I’m still going through the learning what questions to ask phase.1) profits and losses?

We are currently in the diversion phase (30-day Philly requirement before filing in eviction court).

If you want to negotiate prior to contract, most builders are going to do everything in their power to avoid dropping the price...this could mean paying closing costs, pre-paying HOA dues, buying down your rate, giving options/upgrades at no cost, etc...basically anything that is going to allow them to keep the recorded price elevated.Even in down markets we are still trying to show price INCREASES phase over phase, even if that means giving away more in concessions on a case-by-case basis to get deals done.

Or do you require payment all upfront for each phase of work?  

The one thing to consider is how much work your dad wants to do in the next phase of his life and what his financial goals are.

Well, as he stated, it's the funding phase that becomes more tricky. 

We bought from a builder that was in phase 1 of their development.

*I joined this forum for myself, as I'm in the learning phase of my plan to use my divorce settlement to start real estate investing.

I am currently in the education phase of my journey into RE and I am excited to learn as much as I can before jumping in.