., the calculation of tax you'll owe is very straight forward. 

Understand the fees involved and calculate the total cost for an entire year of management so you can compare the different managers.

You cannot calculate rent by subtracting off the rent of the ADU.  

Understand the fees involved and calculate the total cost for an entire year of management so you can compare the different managers.

In this case, since they are borrowing their payments, these would get added to the principal balance each month, and interest would be calculated on that.If, for example, the interest rate on the note were 10%, they would implicitly be borrowing their payments at that rate.

Is it worth to invest and learn from their program in order to start my co-hosing STR side business just to get some extra money monthly?

When calculating your return, bear in mind you'll most likely have to pay 100% in cash to make it work.

The DSCR lender will likely rely on both the 1007 and the AIRDNA info, sometimes at the lender's discretion (which one they will use for income calculation). 

That being said, anything can happen, but if you run your numbers accordingly, make sure that your contractor is trusted and do all the other stuff you'll be a little more protected than the next person flipping that does not do this type of calculation. 

We have a big place so it is families and groups.I do ask guests before booking if they are celebrating any special occasions and I will add some extra things to the welcome box that fits if I can.