Its typically triggered by a third party, so until someone wants to complain, there is no ADA compliance police wandering around giving citations.

Missing these dates can have dire consequences.Schedule third-party inspections early and submit lender applications promptly.

There really isn't any "fair" cut of the profits, it's really just whatever cut each party is happy with.

You also want to think of what the exit strategy is for both parties.

Consider getting a statement signed by all parties which states that everyone has agreed to terminate the current lease early on X date and all obligations by all parties have been paid in full and that the deposit will be kept by the landlord and will be applied to the new lease. 

While that may sometime be true, full disclosure to all parties should eliminate any ethical or moral concerns (imo).  

Get a written quote and have a 3rd party contractor do the work.

The relinquished property was owned by one taxpayer and the replacement property was owned by a different taxpayer, although related parties or entities.

I have people ready to give the funds, I just don’t know what’s the best set up that makes it fair and attractive for both parties.

I would say the cash flow would go up every year and that would usually be the case but my son will be moving into one unit probably for just the labor to rehab the last unit (collected rent will go down for a year).After that rehab is complete, at market rent I would have about $8k/month cash flow with underwriting that most would consider conservative (for example $1200/month allocated to maintenance/cap ex).