Wife also supplied receipts and invoices substantiating the hours she logged” - Source Checkpoint.

It does the application online and we're planning to get Checkpoint Premium screening, then send the lease online also.

Between those two "checkpoints", you can make a slightly more informed decision.

Did you check point of sale requirements ?

Each of these has associated materials, examples, and comprehension checkpoints. 

Too many checkpoints and decision-makers is all PITA.  

It is not like borders between states are controlled with big and beautiful walls and tremendous checkpoints.

I’m positioning myself to do my first flip when I find the right deal and I’m wondering what tactics and strategies many of you use in your rehabs to transition from one check point to the next. 

I stress just as an extra checkpoint but certainly not the place from which to make a decision.

Order and receive an appraisal within XX days.Receive a loan commitment from lender within XX days (or XX days prior to closing).Final funding approval XX days before closing.There may be other "checkpoints" - you need to know your contract inside and out.Finally, to answer your other question: Yes, mortgage lenders will provide a pre-approval letter for an investment property.