It may be cheaper to only increase rent by $X amount, rather than spending tens of thousands on renovations and absorbing vacancy losses. 

Older, cheaper properties in C & D class neighborhoods are notorious money pits.

I don't have a hard and fast, here is what my criteria was when I started:1) Covers enough so its cheaper then renting2) Room to improve rent: addressing poor management or by improving the unit.I figured in my market with fixed debt and rent increases, within 3 to 5 years, the cash flow would be real nice.

Buying a duplex may offset living expenses, and may be a few hundred dollars cheaper than renting.

A/C window units are getting better, cheaper, and more efficient all the time.

Option two would be cheaper from a lending perspective.

The quote was cheaper, service was responsive.    

Refinancing 1 property is cheaper and easier than refinancing 2 properties to get at that money. 2.

Land further out; usually cheaper, but the more rural the harder to get tenants and rent up. 

(Not that they actually set mortgage rates - but they influence them.)You now know that as you look at 2/1 houses that anything priced near or above $145,000 isn’t worth pursuing in the short term… so you look for ones that are cheaper than that.