@Bobby ForsytheI usually rely on the Sq footage to estimate my numbers.

Potentially more if I add some much needed square footage.

Since the reality is a given city or zip code may have quite a bit of difference in rents and property acquisition price from neighborhood to neighborhood, you can often make more than the fair market would otherwise allow for a given area.For the wider market: in some areas square footage is king in other areas bedroom count is king.

Some of my ideas are a simple one-story studio or one bedroom, or building one of those over a garage (to add value while minimizing footprint), but I don't know what square footage or other details I should be looking at to try to reach my goal cash flow amount (after the work is paid off).

Adams County itself requires a certain amount of square footage per occupant; I believe 300 square feet per person.  

I try to keep square footage within 10% or so.The key to the exercise is to eliminate any preconceived notions regarding the ARV. 

Even if you can't individually meter the water, you can do a utility charge back and bill the tenants each month based on their prorated share of the bill calculated using their % of square footage rented.

You can set geographical, size, etc filters on Redfin as a starting point.One thing to note on this, is sometimes it requires a bit of research, in that the posted bed/bath/sq footage on Redfin isn't always accurate, so you might need to cross-reference it elsewhere. 

They can often be a way to add value with more finished square footage, bedrooms and baths. 

I just find homes that have the same sq footage and then take an average of the sale price.