They charge parts only if they do something during normal rotation, or change the pool filter. 

Once you have a shortlist, sign up for an account with each one and test them extensively to see how they function.

In my experience the basics for a functional RE based CRM are:Custom Fields for Data Objects (Leads, Prospects, Applications, Buildings, Units, etc...)A Screening Engine (background/credit checks, employment verification, etc)Online Rental Application (this should automatically run the application through screening)Ability to mass email/sms leads and tenants to provide informationSurveys/Inspection formsI've been building real estate CRM tools for years.

They rotate so that the end of a 12 month redemption period is not in the same month as the tax auction.

These are just very different functions.

Once you have a shortlist, sign up for an account with each one and test them extensively to see how they function.

BP's search function can be likened to Google in it's infancy.

We built out our own portal and accounting database for that functionality because we were not finding good software that could handle a higher volume of receipts AND tie it in with the rental property accounting. 

I like the functionality a lot but it seems that once a month there's a new bug to contend with that's eating into my time.

I never used it in the way you are describing but I can attest to its functionality.