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? 

A true recipe for financial disaster.

If it’s doable financially I’d recommend the duplex.

If two funds need money for litigation support, that seems telling on the current financial condition.

Not because we had failed - this was a four-year resident entering their fifth year on the property when they got into financial trouble. 

With that in mind, I’m considering purchasing four rental units over the next four years to build a stream of income that could help supplement my retirement by age 68.The challenge I’m facing is that the deals I’ve come across so far don’t make financial sense.

A couple of things I like to tell my newbies-Owning a short-term rental property can offer significant financial benefits.

What financial targets do you have?  

With the future being so uncertain I realized there was a need to do more than just rely on my job for financial security. 

It’s important to ensure you’re comfortable with these risks and consult a financial advisor.If you choose to use a HELOC, consider traditional financing or private loans as alternatives if you prefer not to risk your home.As for your first rental, markets in the Midwest and Southeast offer great opportunities with turnkey properties that are tenant-ready and appreciating.