They have not returned the keys yet and the utilities are still in their name. 

I have 250K on a line of credit with interest at an Annual Percentage rate of 5% that I can utilize.

I'd say an estimate of at least 10% Capex/Maint is more common in evaluations.

My first question, is: Is it common to find a 30 year Finance on an investment deal?

1) Previously 50% utilization on each credit card (not aggregate of all cards) is now 30% to have an impact on score2) They now look at "payment acceleration" meaning paying the minimums every month is looked down upon..

Is it common to give experienced developers such a premium for their sweat equity?

Seeing as I have not met him, is this common practice?

How do your earnings compare to a long-term rental where the tenant pays for utilities and landscaping?

Because I will have a full-time job in a year, I plan on utilizing the buy & hold strategy on SFRs and multifamily properties.  

Only thing I take from the seller is the actual utility bills.