I am trying to evaluate 38 separate homes, is there a tool, spreadsheet or software that I can use to input all my data to come up with ROI or do I need to write my own?

Lots of great data in there for you.

The difference is that in years preceding a dip, a CA asset will appreciate significantly whereas a midwest/rustbelt property will not.Check out some of @neal bawa's webinar's and data points, specifically "Real (inflation adjusted) Price Gains".

You can also contest the appraisal if it comes in low (done that myself before), so be prepared to present some comp data, just in case.

The ARV will perhaps be the easiest and closest thing to which you'll have data for. 

@Ed Morrison Rentometer has a pretty horrible data model.

(i.e. are big complexes or small ones driving the data?)

Whereas the vacancy rate increases so does the median cap rate.The data above was collected from the census american community survey and is computed at the tract level.Vacancy rates where computed first and split into cohorts that increment 0.1 percent.

Maybe they think they're being helpful, but it's actually quite the opposite.I work in data analysis/research for a living, so I'm pretty anal about this stuff.

I get all the data from my real estate agent.