However, its downfall (and really what makes it so easy) is that it is a single-entry system. 

In the last few years, they've made illegal:-Rent controls of any kind-Limiting of fees or screening charges-The ability of HOAs to regulate STRs or LTRs in their neighborhoodThat's just the start.

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Most businesses, property management or not, fail due to the lack of sales, not due to the lack of systems and phone etiquette.

Totally out of control.

I'd like to speak to the it's the owner not the dog, it's a bit like the gun control issue.

What do you recommend for hot water leak alert system?   

If one or more units are vacant, the remaining units often don’t provide enough cash flow to cover expenses, making it harder to meet operating costs.Maintenance costs: A fourplex comes with four times the appliances, plumbing, HVAC systems, and other components to maintain, leading to significantly higher repair and maintenance expenses than single-family homes.If you want to see the detailed calculation, read this BP blog - More Units Doesn’t Mean More Money—Why a Single-Family Home Can Beat a Fourplex.Resale value: Multi-family properties have a limited buyer pool—mainly investors—who base their offers on CAP rates.

The members here on BP that talk about STR auto-run systems didn't install those systems and find dependable cleaners & handymen overnight.

Rent control on MF and if prop 33 passes (last polling I saw had it ahead) it could apply to all housing.