If one of the contractors lapses their coverage and an employee is injured, they may be able to go against your coverage as GC.  

If a sub gets injured on site does that fall on me as homeowner or acting GC?

He's going to stammer and be embarrassed and have excuses but you married him, time to get him cooking bacon or if he is mortally injured to release all liens and get someone else started today. 

@Gayle Eisner.... your are talking more about personal liability.....someone gets injured and they go after you.

And do not even think about using the illegal basement as-is...imagine a fire breaking out and someone getting injured or worse....that would all be on you.

@James Hamling1,000 people die per year from a lawnmower, so should you hire someone to do it for you.If you own in a really bad area or are just a bad tenant yes your chances of getting injured go up significantly but just as many realtors are probably killed per year as landlords which I bet is less than lawnmower deathsOh and those deaths are typically at the property not the tenant stalking the homeowner.

A PM won't see a board from the roof of a house that has come loose that could fall in a tenant and seriously injure them.

High risk of being injured - maybe permanently.

Otherwise, if you hire day laborers or other handymen, if they get injured, you may be liable for their injuries as their "employer".  

Also good idea is to get a verification that they have their own workmen s comp insurance, so your not stuck if they get injured on your site, you simply ask them to have their insurance guy send you a certificate of insurance made out to you, for your address your having the work preformed at.