I think you can go as high as 15% but it's cutting into your margins and depends if you are a GC yourself or not. 150k is close to a million or more.

There are a plethora of CT based real estate Invetsor meet ups you should get involved with.

Where are those areas for you?  

Most homes in our area double in value every 5-10 years.

Quote from @Jordan Laney: I would call a couple snow removal businesses in the area and see what they would charge for that..

Anything bigger or in a nice area, could multiply that amount. 

Check the forum for Events & Meetups and see if they have any in your area.

Here is one piece of advice When looking at areas to invest in check out this website https://www.areavibes.com/ its pretty cool it gives you a total livability score and rating for that areaBest of luck!

Petersburg area, resulting in highly–profitable investments.If you need professional and courteous property management experts for your multifamily, single family, condominiums or town home, you've found the right company!

These areas are currently great LTR and MTR areas!