Rental Empire: what you wish you'd known for financing ?

[Ben Magee]

My wife and I just finished our first BRRR deal on a single family residence. We're looking to get smarter as we get more rentals and wanted to ask y'all for help. I wanted to see if any of you all have guiding principles on these areas of thought: mortgage length, paying extra on debt, selecting your first couple owner occupied homes, and other thoughts.

1) 15 year mortgage or 30 year mortgages? To frame this one, the question I'm asking is if you could be close to breaking even with a 15 year mortgage or you could be cash flow positive, which one would you take? If you take the 30 year, you have more of a cash providing asset. But if you want to get your asset paid off and maybe paid off before things like the roof and other stuff wears out, maybe the 15 year would be the better route. 

2) Do you want to put extra towards your mortgage ever to save on interest for these homes or do you put all that money towards getting more homes? 

3) My understanding is a bank will loan you up to a certain number of homes (4 maybe) and then they are gonna not be so inclined to keep loaning to you and maybe make you do investment properties. So my wife and I have wondered, 

a) should we try and buy the most expensive house we can (that's still an asset producer) with the lease money down, so that we can later sale those for the most cash and use that money to buy more rentals.  Basically, you could buy 3 houses that were 200K each, or you could have bought three homes that were 350 K each and later when you sell the 350K ones, they have more profit if appreciation worked out, to be used for investment purchases.  

b) should we try to climb the multifamily ladder instead (duplex, to triplex, to quad,...) ? 

4) what else are we not thinking about that might be worth thinking about (taxes, timelines etc)