The math is easy, the 1st Lien Heloc, even at a higher interest rate, will out perform a traditional mortgage hands down with respect to gaining equity/wealth much faster, with no change in household spending habits. 

Doing so would be a prohibited transaction because you are a disqualified person with respect to your plan.

I use it, though I hate it, but I avoid problems by setting criteria such as how much in advance a party has to book, minimum number of nights, requiring either a large deposit or purchase of insurance, house rules & photo id requirements prior to arrival, withholding check-in information until just before arrival and sending it to a verified cell phone number.

Years of tenant screening has earned me a house full of non-whining, flexible and tolerant low-maintenance tenants that respect my properties and auto-pay their rent.  

I can't tell you how many properties have units easily convertible from 1 bedroom to 2 bedroom units, units with favorable dimensional standards which can boost rents with no photos to showcase these attributes, assessment square footage that is not correct,  upgrades not identified in the marketing materials etc.

Guest takes more care of the property, since you,  the host, are the only judge to decide if you retain or not the deposit in case of damage or issues.Another Good: You can write in your contract that non respect of rules may lead to lose some of the deposit: Like noise, or a very unclean check out, etc...

Photos: Yes, taking photos of everything before your tenants move in is a smart move.

Take photos of the condition the tenant left it in. 

I just ask for a photo ID at time of booking.

They are known for their thoroughness and provide clear reports with photos, which can be really helpful.