Make sure there are no Federal Pacific electrical panels. 

I also have some cash reserves that I plan to dump into a contingency fund for each unit. 

I used a HELOC to cover the down payment, appraisal gap, and furniture, allowing me to enter the STR market without depleting cash reserves.

Avoid common pitfalls like skipping due diligence, underestimating repairs, and overleveraging having reserves and a strong team is key.Good luck!

If you find an actual property that looks like a homerun and would warrant a HELOC, then you can go for it without reservation.

I would consider selling one of the properties, paying off the debt, creating a reserve for your remaining investment, and ensuring you are 100% financially stable before you invest again.

However I like to run my numbers conservatively and account for cap ex, vacancy, maintenance reserves 10/5-7/5-7% respectively.

The best references I could find would be from the Federal Reserve Banks themselves. 

I would have reserves beyond that though.

However, federal securities laws and SEC regulation require providing investors with accurate information regarding investment risks, details, and fees to prevent fraud.