This percentage will vary per investor, but somewhere around 5-10% seems to be the general rule of thumb.I would require your tenants to pay for their own utilities. 

Most lenders will count a percentage of the income from the property toward your debt to income ratio.

Here are a couple of numbers I use -- and many other investors too -- although others may prefer to tweak the percentages a bit for their style or individual market.Flips or rehabs --  Take the After Repair Value of the home (ARV) and multiply it by 70% and then subtract the rehab.

If I outsource then what percentage should I ask from the auctioneer?

Ask how many or what percentage of owners are delinquent on there fees.

The builder's estimate of return on money after the two years is thus: when refinanced and rented out (builder estimate) an 80-90% return on investment and you would still hold your percentage of ownership.

Is there a safe percentage?

There is a small percentage who do the job correctly and create value on multiple ends.I think Rick H. said it best, some people trade equity for piece of mind.

Loan to cost means that percentage is only based on how much it actually cost you.So in your situation, they would completely disregard the ARV, they would be loaning on a percentage of the $105k you have into the deal.  

How much mortgage would the owner hold and at what percentage?