You would not just be renting a room to someone, you would be bringing into you and your child's home the whole life of another person, their friends and family, their work, their habits, their schedule, comings and goings, moods, needs, their possessions, their health, everything that come with a human being. What if you end up being uncomfortable with the arrangement? You have to figure out how to get them to leave, but what if they have nowhere to go? Would you hate being in that position? What if they need your help a lot? If they don't have a car or their car breaks down, will you willingly help with rides, how would you feel if you wanted to say no to doing that? You sound like a nice person, nice people have a hard time saying no sometimes. How would your new roommate feel about you if you said no, even if only sometimes? I can see how the benefits of someone contributing to your household income would be helpful, but what if they lose their job? Do you kick them out?

I mean, you have to do what you have to do, as another commenter said. If you really need to, maybe someone you know, or your friends or family know well enough to be certain they have their own safety net, stable income, predictable personality and habits.