If I had a 3 bed 1 bath on both sides of a duplex and a 3 bed 1 bath single-family home in the same neighborhood how different would the rental rates be? I'm assuming you could get more for a single-family verse multi-family? Why exactly is this? I am trying to determine what to set my rental rate at when doing property analysis but a lot of websites / tools for that are geared towards single-family homes.

The best way to know is to check your local rental listings and get a feel for what each goes for.

Your area may vary, but typically a home of the same size would go for a couple hundred dollars more per month, because people like living in their own home rather than live right next to the smell of 420, loud parties, and drive-by moonings (no personal experience here).

People generally prefer having their own space that they don't need to share. To a small extent this is a little different with single millenials who like living with one another, but that's the exception.

Families are almost always going to want their own space. They might like the neighbors but many of them will pay money to NOT share walls.

Of course, at some point a lower price is just going to attract people.

Quantifying this is a completely different thing. Rentometer.com will never be perfect, and this calculation seems like the hardest part to accurately assess. Glad you asked this question, because from BP podcasts and webinars, I am frequently wondering how one can send out so many sight-unseen lowball offers (Brandon Turner's "The Funnel") without putting a ton of effort into really hammering out the rental rates.