@Sebastian SoveroThere are 3 main parts to a seller financing deal: down payment, interest rate, and price (4th would be the term).

I vividly remember the countless hours spent driving to and from remote locations in rural Manitoba, alternating between early BP podcasts and Jim Rohn recordings.Over the next two years, I adopted an extremely frugal lifestyle, enabling me to achieve a 75% savings rate, sold my custom truck for a used Toyota, traded my new home in the burbs for a duplex (house-hack) in a challenging neighbourhood of Winnipeg where attempted break-ins were commonplace.

Assume a 10% (pulled out of the air number) interest rate on the heloc.

He would be safer in a savings account at that rate (I know what you're thinking... appreciation, though).

Nobody knows lead conversion rates, except maybe the company who is converting them. 

As mentioned previously, some HOA's charge a fee every time you rent and this could influence your bottom line.  

She has been worth her fee twice over, and has helped me a lot.

She has been worth her fee twice over, and has helped me a lot.

(Floating rate loans, with no rate cap) 

I keep wondering about insurance, vacancy rates, if tenant selection is a bigger/ different factor, terms of the tenancy and differences in opex and capex?