It requires using a home automation platform (I use hubitat), creating an API, and creating some rules within the automation platform. 

Don't focus on a "rule of thumb" as a rookie.

Consider the "2 of the last 5 year rule" to avoid capital gains.

With the economy of scale in multifamily, each additional unit nets you a little more than the last, as a rule of thumb.

Make sure your listing clearly outlines your screening criteria as well as your "house rules" if you're renting out a single room in your home.

Sharing understandings and rules on guests, cleanliness, chores, pets, drinking, drugs, boundaries, house identity, conflict resolution, communication platforms, etc.

For existing properties, you must make substantial improvements (equal to the property’s value, excluding land) within 30 months.Ensure the duplex qualifies as an OZ investment and complies with QOF rules.

Each town has different rules regarding rent control. 

Asking in the correct forum will get a better response.Read the RULES!

You can still find positive cash flow and deals that do hit the 1% rule here!