Highly recommend you connect with him if you haven't already. 

:Class A Properties:Cashflow vs Appreciation: Typically, 3-5 years for positive cashflow, but you get highest relative rent & value appreciation.Vacancy Est: Historically 10%, 5% the more recent norm.Tenant Pool: Majority will have FICO scores of 680+, zero evictions in last 7 years.Class B Properties:Cashflow vs Appreciation: Typically, decent amount of relative rent & value appreciation.Vacancy Est: Historically 10%, 5% should be applied only if proper research done to support.Tenant Pool: Majority will have FICO scores of 620-680, some blemishes, but should have no evictions in last 5 yearsClass C Properties:Cashflow vs Appreciation: Typically, high cashflow and at the lower end of relative rent & value appreciation.

The high season is May/June/July/Oct.  

What do you do to revenue predictions to account for the fact that some owners don't set prices high enough to the market rate, or set them to high and don't get booked as much?

but if they cannt afford 20% down ($60K), they are a high risk of not making payments; and there are legal costs to foreclose and get your property back

You can't give up even after days/months of not producing results, which is highly unlikely. 

What is the rate/structure of the loans on them - is this Hard Money - high rates?

It seems quite high to me, especially considering I'm still relatively new to this field.

If the loan amount exceeds $1M, then rates are in the high 6's to mid 7's. 

Above ground, unless a huge amount of great landscaping (and high maintenance) would be need to make it pleasing.