With the frequency of phone number changes that people sometimes make, this has become a challenge for us.

It happens at a much higher frequency than you might think.  

I am also interested in groups that can not be tied to a single location but may meet via a web based medium at a regular frequency. 

Unless you've lived in one of those markets before and really know it well, you're not gaining any advantage by investing where friends and family live - you'll be hiring a PM that knows the area, and you shouldn't have to check in on the prop physically with any frequency unless you just want to.

If my numbers show 33% DTI but the official software says 47% (happens with shocking frequency), I know that one of the two is obviously wrong, and I know this early in the process.

If the goal is the long term play and money isn't a worry, it is more about the structure and content you are going to push (having a plan for it, frequency, content), rather than exactly what company you use to do so. 

Adjustable Rate Index: One Year T-Bill (1 Yr C T) Change Index: 2.75% Rate Change Frequency: Annually First Change Date: 11/01/2010 Int Rate not <: 2.75% Int Rate not >: 10.87% Maximum Interest Rate: 10.87% Interest Only Period: Prepayment Penalty Rider: No Prepayment Penalty Term: Mortgage Record Recording Date: 07/31/2001 Document #: 2001-222392BK-PG - Loan Amount $211,500 Loan Type: Unknown Loan Type TD Due Date: 08/01/2031 Type of Financing: Interest Rate: Lender Name Lender Type: Lending Institution Borrowers Name Vesting: Joint Tenants Prior Transfer Recording Date: 11/07/1989 Document #: 15463471 BK-PG - Price: $220,000 Document Type: First TD: N/A Type of Sale: Mortgage Doc #: Interest Rate: Lender Name: Buyer Name: Buyer Vesting: Seller Name: Legal description Abbreviated Description.

If, on the other hand, similar deals at that price are so rare that you'll never find one (or not in the time frame you or frequency you need), then the offer price is probably ridiculous.Investors WILL sometimes find deals at "ridiculous" prices for their area.  

The frequency of the subject property being a deal is probably lower then if you went with some paid sources but we make that up with volume of analysis.

Also, be sure to ask any PM's you're interviewing about their tenant screening, frequency of evictions, and their late rental collection/eviction process.