AirDNA and other sites are not going to be able predict what kind of an STR host you are going to be, what kind of exact experience or amenities you are going to provide, all of which dictate your reviews and consequently your booking performance. 

Groundfloor recently posted an empirical analysis of estimated ARV for all loans that subsequently repaid in 2018.The data shows that the median predicted value was 4.7% lower than the sales price, while the median appraisal value was 8.6% lower.

Alex your betting alot and trying to predict the market.

Thats assuming you can predict the future and maintain a good rental history. 

The folks who claim to have predicted correctly in the past generally are confusing luck with a prediction.

That makes it tough, tough on the newbie but also not easy for me.For appreciation, the best is accurately predicting the next hip area but without a crystal ball that is difficult. 

But assuming that the first year is predictive of the following years--and this is a big assumption, you better watch out---then it tells you that besides everything else, the investment will not be adding to your liquid cash, not draining it, returning 10% liquidity to your cash invested per year.The idea with many investors is to put as little down as possible. 

Long story short, knowing the historical rates are beneficial but it doesn't necessarily predict the future rates of the market.

What you want is a predictable, consistent monthly payment.You should do a refi of house "A" to pay off the HELOC and move into a 30 yr fixed.

Specifically, were projected returns fully realized, were fees and other charges excessive, were holding periods predictable, etc?