Some are just quicker than others.

A non-bank lender will be more expensive in fees & rate but they'll be able to close quicker, require less of you, and offer you a 30 yr fixed rate off the bat.

Rehab investing should anticipate months wait for a good contractor to rehab the home, or for a quicker hire, shoddy work.

The requirements/underwriting process will be much easier and quicker than working w/ a bank or more traditional source of financing.

The earlier you start, the quicker you'll get to your goal.

However if you borrow against the 1st house you have the cash for a quicker close and can buy properties that can't be financed.

That difference will get you out of PMI quicker so pay the extra, then hold the loan; at 2.375%, that's free money.I see no reason why not to go with Rocket, your local lender is going to sell that loan on the secondary market anyway. 

Personally, I would offer them cash 4 keys to leave as it is cheaper and quicker but they will probably all talk and all refuse. 

A background in those areas saves DD expenses and brings quicker decisions.

I'm looking at some nicer houses move-in ready to build quicker and don't have the 50k needed for down payment and closing.