My wife and I are currently renting in a B+/A area which she doesn't want to move from.

Obviously it isn't as easy as A-B-C and I have a lot more to learn, but I am just getting started.

I've fix and flipped 1 - 3 unit homes but now I'm turning my attention towards 4 - 20 unit apartment buildings in good areas. Would like to know what are best cities for investing in apartment buildings and where good...

.$1500 in rent and income of $4500 is not above average for a B class rental area.

The big thing you will have to decide is whether you want to buy in an A class neighborhood, or if you want to buy in a B or C class neighborhood where you get more cash flow but its not as trendy. 

Just want to find a property in decent shape that's in a B class neighborhood. 

Be patient, if it is a B class property your screening standards are acceptable.

For example, I consider my primary residence to be a B/B+ area -- my house is worth $400K, but the few rentals in my neighborhood are only getting about $2000 in rents. 

Under California law (AB 1482), annual rent increases are capped at 5 percent plus the change in the regional Consumer Price Index (CPI), or no more than 10 percent of the lowest gross rental rate charged the tenant at any time during the twelve (12) months prior to the effective date of the increase.

It might work for you, and 6 years ago i would totally be 100% in on this, but I couldn't in good conscience tell anybody that you've got a good chance of having a BS-free successful experience buying HOA liens right now.