Airdna is your best place to gather actual numbers, although you do need to know how to use the software, as well as talking to neighbors in the same complex with a STR. 

TenantCloud is cost effective, starter property management software you are can with.

There you go, submit your bidBut Privy already does that and few other software too.

What websites or software do you find most helpful in general when investing in real estate? 

Quote from @Jay Chung: Software is a common question on BiggerPockets.

I can think of mortgage, taxes, insurance, STR insurance, water/sewer, electricity, trash, internet/cable, cleaning (can pass through), supplies, and software.

There is also a software named LandVision from LightBox that has a good layer that lights up every parcel that has traded in the vicinity and timeframe you are looking for/in. 

I have managed my rentals on a very basic spreadsheet (poorly managed) and it is time to clean up my accounting and legal structures.Can anyone opine on a cheap and effective software for the accounting side of the business? 

If the system is not user friendly, people will move to simpler softwares. 

Overall, it's an easy to use software with a great UI and free property data.