One of the biggest unaccounted expenses can be your personal time.

If you want to self-educate, there are an insurmountable number of posts you can find by searching BP, either with the magnifying glass above or through google.You don't need lease agreements between you, the LLC, and the bank.Just keep track of airbnb revenues, rental days, and all expenses. 

That's the single biggest thing causing high housing costs in the expensive coastal cities. 

My biggest setback is my income. 

You can attract some of those same tenants in outlying areas as well (think Nike/Intel)...biggest hurdles are future of landlord tenant law in Portland.

One of my biggest hold backs from early retirement is healthcare/insurance costs.

Overall I think the biggest winners of this mess are the politicians pandering for votes. 

So he has 100 x $700 x 12 = $840,000 of revenue and an expense ratio of about 60% (he is a contractor and does all the work himself).

My biggest interest is that I'm able to sell after 10 years and take advantage of the appreciate exclusion.

Biggest question I'd ask is whether or not I could afford the additional payment without relying on income from the investment property.When looking at a potential investment property, look at best case, most likely, and worst case scenarios and decide what the probability of loss is.