The risk of "piercing the veil" applies more to LLCs when personal and business finances are not properly separated, not necessarily to individual landlords renting a portion of their home.A more practical approach is ensuring you have a solid lease agreement, sufficient liability insurance (including an umbrella policy), and properly reporting rental income and deductions on your tax return (Schedule E).

Set on 3.3 acres, this home has everything your buyers are looking for: a brand-new septic system, a state-of-the-art wall-hung boiler with radiant heat, and a stunning new kitchen complete with updated appliances and an island for gathering.

Thanks @Kerry Baird, I was talking with ridge lending and they have recently stopped the all in o e heloc product.  

That usually creates a big supply of rentals on the market that it 's hard to be absorbed and create a race to the bottom in prices, as all the properties are pretty similar and in brand new condition. 

I know that the general guidance is that emergency funds aren't to be invested, but given our financial security and the fact that we already have a personal e-fund in a safe, non-volatile location, would it still be crazy/unwise to invest this 15k in an S&P500 index fund in a brokerage? 

Quote from @Greg Scott: Quote from @Derrick E.: I always play it by ear.

Have a big database, sellers who look up my brand/appeal.

You can however, write off the other unit as a rental on a Schedule E.

Even trusting a brand new GC who's licensed/"qualified" is a risk from out of state, let alone out of country.

You must report rental income on Schedule E and can deduct rental expenses like repairs, maintenance, property taxes, mortgage interest (allocated between personal and rental use), and depreciation for the rented portion.