We need to “special needs” proof

My son has down syndrome and has fallen in the autism spectrum. He has very little speech . We love our boy and he is amazing. My husband and I are going through hard financial times and we have other children. We married a year ago and since then he has been laid off. One income and it's been tuff. My son escape our home and runs off. I'm so worried for his safety . We try locks and he has learned them. We have since added more higher locks. I would really like to fence off our front porch, just mainly around the front door to the fence line. Where we can lock it, another boundary incase he gets out. We live on a road where everyone speeds. I'm so worried for my son. My other children sometimes forget to lock the locks on he front door and and a gate would be another step he would have to go through before we notice he's gone. Yes i watch my child, but sometimes you have to go to the bathroom, cook dinner, take a shower,etc. I'd like to put alarm devices on my doors and windows because he is exploring his options, any money left over will go to speech therapy resources. The money will be used to gate the front of our home with locks, but locks on our windows, secure the back doors and back fences. The child proof our home for his health. We have mildew in places turning to mold. I really want the best and work hard but I'm turning to ask for help as my son made it outside the other day and we found him safe but it could of not ended that way with ditches nearby and the cars that speed down our road