When you eventually get a deal under contract and only have one lender if the lender decides not to do it then your stuck. 

I intend to do rental arbitrage to start and then eventually purchase.

So if it comes to starting out like you said, I do believe single family 1-4 units is the way to go until they can eventually build up to get to multi family. 

Some people get lucky and enter the game when everything is easy to sell, but the market eventually dries up.

Although right now is a fairly tumultuous time to get into the space I would do what you can to dive into education as to how to evaluate deals and what you eventually want your portfolio to look at both in terms of composition and risk profile. 

A lot of duplexes listed are way overpriced and if you can find one thats listed over 60 days you can probably win an offer eventually with that strategy as well (I almost got one like this as well on loopnet).  

“Will I eventually be able to raise the rent some?”

My bookkeeper will know that any transaction from that checking account is associated with that specific property and eventually they all come from there.

You’ll eventually need boots on the ground (core 4).

best tip is to put all your housing on their website https://www.alesolutions.com/register-housing/ and then if someone eventually reaches out - just own that relationship.