Preapproval Process: How to Finance?

[Q Johnson]

Hi, 

I am new to REI and I have inquired about and analyzed several deals. I spoke to a buyer's agent who informed me that I need to have a pre-approval letter prior to any showings; and obviously, prior to any serious consideration via contract.

I reached out to a Real Estate Agent that I am developing a relationship with and she recommended a few loan officers/mortgage bankers. 

I do not want to put down on a property today, so to speak, but I have been saving and I want to put myself in the best position as I am looking for a deal. My current/initial focus is a SFH/small multi-family unit rehab project.

I am seeking insight on what questions to ask during the pre-approval and financing process and what to expect from the bank's side? Also, if I buy a rehab with cash, but I will need financing for the rehab/repair aspect, how does that process work? 

Thank you!