How best to decide on major CapEx expenses (ie, vinyl windows that may last 20 years but are cheap vs aluminum that may last 50 but are expensive)How best to handle what happens if/when one of us wants out of this in the future for some unforeseen reason?

As far as regular contingencies, those should be rare - like something totally unforeseen came up during an inspection -- then yeah, that is what those clauses are for.Wholesaling is really, really, really hard. 

I am also going to be  3 months over on my rehab due to unforeseen structural issues.

Just wondering down the road if there’s any unforeseen problems with doing that.

In case of something unforeseen, you should have escape clauses in your contract.

The biggest issue is that this is the riskiest of all the real estate strategies (opportunistic) even for very experienced operators, because of all the unexpected and unforeseen things that can go wrong.

Off market is great, but build inspection/finance contingencies into your offer just in case there’s a hidden lien or unforeseen repairs that would show up.

This can add quickly to unforeseen expenses during a flip.

I don’t want to use all of my cash one 1deal and not have anything in reserves to cover any unforeseen expenditures. 

The renovation costs may include a contingency reserve and renovation-related costs.Contingency Reserves: Contingency reserves 10 % required for any unforeseen cost overruns that may occur during construction.Unused contingency reserves that were financed into the loan will be applied to the principal balance of the loan.