I find it's very personal, and dependent a lot on your goals, resources, risk tolerance, location, experience, etc.

What location?

I have seen this same house that is vacant (all the classic signs) I have located the owner ( I have not reached out to her yet).

@Polat CaglayanI've never seen a formula but here is a general rule of thumb for multifamily:The class of an apartment refers to the quality of the building, which can be determined by a number of factors, including age, location, and condition: Class A: These are the highest quality apartments, typically built within the last 15 years.

We found an opportunity to purchase a huge SFR with two kitchens located next to a commercial zone which was previously used as a sober living facility.

You want to be close to RTP (our economic hub) and the airport (located right by RTP).

I am located in north Jersey 

WHat are these locations?

Since comps are limited, analyze similar nearby locations to estimate demand.When pitching investors, focus on a clear business case: expected income, expenses, occupancy, and ROI.

Sadly, it seems that cash flow on long term rentals with 20% down just does not exist in most desirable locations.