I personally use Hospitable for hosting, it integrates with my Schlage Encode lock and automatically generates door codes.

Also, any recommendations for good zip codes to look into?

  :)I reread some of my post and wanted to add something: One main reason to make sure to get permits "finaled," is some building departments may make you bring the work up to current code, when you try to get a final inspection.

I probably have a promo code I could give you if the BP one isn't good anymore but I used the free version for quite a while with success.It's also pretty decent at pushing listings out to some of the major rental sites.

I’m looking at multi family units and mainly curious if certain zip codes tend to have more troublesome tenants vs others. 

The areas you mentioned have opportunities, I also like zip codes 93710, 93728, 93704 as there are a lot of homes in the price range you mentioned. 

The best way I know is to use airdna.co for some local/zip code level research. 

As long as they are to code and removable, I wouldn't have a problem with it.

Per the Land Development Code transient rentals are allowed in the following zoning districts: R2, R3, R-TH,CL, CM and CH (R1-C if south of Front Beach Road)

Or is this something that can easily be brought to code?