Your son should look at some very family friendly areas first (try North Shore area---I am very partial and it has a lot to offer.)
Find a good realtor. If looking in North Shore area, try Deb Terlik at Keller Williams in Beverly. We ended up buying our house from one of her clients and I was really impressed with her.
The realtor should be able to steer your son to some good properties. When filing out the application, he should be as honest as possible and let the realtors and landlord work out a fair deal. Most landlords would be understanding in this situation. Just be ready to negotiate.
Things he may consider negotiating:
---sign a 18 month or 2 year lease (landlords love long term rental).
---offer additional escrow.
---pay first two months up front with the escrow.
---offer to pay rent on the 15th of the prior month (so he is always 2 weeks ahead--giving more than ample notice to landlord if there is trouble.
Most landlords want good tenants and a lot of tenants are renters because of a credit mishap. That is the reality of today. If your son has a good realtor working with him and is willing to negotiate, he should be able to find something suitable.
Let me know if you need any contact info for realtors. I have worked with many and there are a few good ones out there and some really bad ones too.