My question for anyone who has experience estimating is, how accurate and reliable is estimating by sqftage, and what other forms of estimation would you reccomend?

Interestingly, they aren't the least bit interested in my places at the accurate rent, just the cheaper ones.  

If you look closely, the MLS has a disclaimer on it that data may not be 100% accurate and should be verified.

More accurate.

BUT, if your FMV and condition are accurate you have $5k-$15k of equity built into the property.

Lima does compete with Black Rock and 3 others that do similar business  but they are not the most cost effective.As for the numbers...You buy a house for  100K with hardmoney in Tacoma .....maybe you put 20K down so you owe 80K to a ((SHORT TERM 12 month)) hard money lender as  all the windows are busted and it is a mess and at that point only worth the 100K you paid.....but in a great neighborhood of 200K homes.You spend 30K on the Repairs......If you hold it 90 days....and you are now in title ....After you fix it ...It is then re-appraised........once it all pretty and has a tenant in ....for a new fixed 30 year loan based on it FINISHED A.R.V. value...Your new REFINANCE  loan is based on 75=80% of the  ARV finished value.....which I hope is about now worth 160,000 - 170,000.ooSo 75% of the  new160,000  = $120,000 new loan amount.....which pays off your hard money loan of 80K and the 30,ooo repairs your put in ,....and almost all your down payment.You have now recovered all your costs in  place....and have a fixed loan covered by the rents...Wash Spin Rinse Repeat.....As for the Rates..we are both a FNMA lender and commercial lender....so these are accurate..1) FNMA owns 80% of all residential mortgage paper in this country and 30 year fixed - Full Doc loans at 3.75% to 4.25% => Credit Union and Residential A paper lenders VA -FHA -USDA etc2) Commercial loans - 30 year am 5,7, or 10 year term = full doc loans price with good credit price at 4.375% - 5.5% ==> Think community banks and big 5  - WFC  - BOA - Chase etc and local Portfolio S+L's and some Commercial Credit Unions....3) Stated Income Hedge funds....30 year fixed - No Doc  or  Low Doc with Great Scores ===>  loans price at 5.75%  - 7.5% ...think Black Rock, Velocity,  Lima,  RNC and others4) Hard Money = short term to 3 years....prices at 8% - 10% There are no hedge funds or finance companies like Velocity or Lima or RNC or  Blackrock that will make you a  loan < under 6% as they need the 300 basis point spread over the 10 year commercial swap rate to cover their cost of funds...regardless of L.T.V.I get wholesale rate sheets from some 30 lenders a day/week....and that is the risk/reward spread.Hope that helps explain the process and the tiers of lenders...

Can anyone recommend an affordable yet accurate skip tracing company/site?

and in the future which might be more accurate to use?

If these assumptions above are accurate, i would have walked.You can easily locate deals requiring less than $5k rehab and more than $1200 in rents.  

This means you would need a detailed scope of work and would need to be able to accurately determine how far along they are with each task- percentage wise.