The original loan will be paid off in 5 years, then the only expenses will be things like repairs/maintenance, property taxes etc - haha, or is there something I'm missing and not thinking about? 

I know what the rents should be for each of the units (2 vacant and 1 significantly under market), the taxes are listed on the MLS, I’m familiar with the water/sewer costs in close proximity to this building, and I know what percentage to use for my Vacancy, CapEx, and repairs and maintenance based on my knowledge of the local market.

We (the buyers) notified our agent that the property must also be move-in-ready.We received images of the interior and exterior which showed the property in move-in ready condition/what appeared to be minimal to no deferred maintenance issues, the listing said "property inmove-in condition/turn-key".

Certain expenses are all lumped together for the sake of the P&L like insurance and taxes and others like repairs and maintenance can be viewed collectively or by individual property.

This is an issue in Reno, NV with many multifamily properties where an older owner has not raised the rent in years and their selling agent thinks the property is worth market value, it's not and there is usually lots of deferred maintenance.

Those buildings won't maintenance themselves, nor should the tenants be responsible for your upkeep!!!!

Monthly expenses will include mortgage payments, property taxes, insurance, utilities (if applicable), maintenance, and reserves for repairs.You’ll need at least 3.5% for an FHA loan or 20% for a conventional loan, plus cash reserves.

Taxes, interest, insurance and maintenance will eat into the profit. 2.  

However, it can come with extra costs for setup, maintenance, and potentially higher interest rates on loans.

Better cash flow and less maintenance than renting the whole house.