Duplex Financing - Better to put less down?

[Alyssa M Saylor]

My offer was accepted on a duplex and I'm super excited! I will be living in one unit, inheriting a tenant and continue to rent the other unit at $700/month. I was curious to see what your advice would be in regards to how to finance it. 

I was expecting to put 20% down until I started comparing lenders. One lender offers a first time home buyer option. This is the lowest interest rate I've seen at 2.875% but you can not put more than 20% down. He suggests putting only 10% down (or I could put down less if that is what is recommended by BP!) This does come with PMI which is estimated to be somewhere around $30 a month. So let's break this down:

Lender 1: 

10% down. 2.875% interest rate. Est principal, interest, and PMI: $538
Insurance and taxes will be roughly $337. So in total my monthly payment would be about $875

This lender has another financing option. 
20% down. 3.375% interest rate. No PMI. Est monthly payment with everything included: $818/month.

Lender 2:

I got a quote from a second lender and if I put 25% down, I can get a lower interest rate at 3.125%

25% down. 3.125% interest rate. Est principal and interest: $437
Insurance and taxes: $337 Total monthly payment comes to roughly $774

That's a hundred dollar difference every month from the first option to the third. What would you do? Is it better to put as little down as possible if you're looking at it from an investment point? I plan to be here no longer than 2 years before I buy another duplex. (There's one right next door that the seller also owns and I'm hoping she sells it to be eventually).