Jayne, I work with these kinds of challenges all the time and as a broker have access to hundreds of national lenders.
A credit score of less than 620 is very difficult to get approved and it would be "best" if you were not on the application. If you are not on the application there is no way to "count" your income. Your son and husband would need to qualify with just their income. Increasing the challenge is that Washington is a community property state so lenders are required to add any of YOUR individual debt into the equation - your debt is your husband's debt.
I do have lenders who will consider credit scores of less than 620 but it is not a quick process - and anyone telling you it would be is just not being honest. It might not even be possible as the credit score itself is just one of dozens on criteria the lender bases their decision upon.
In my opinion I'd try to have your husband and son make a full loan application first and see that through until that is proven not to be an option. If it's not, then I'd add in your information and work with a lender who has access to sub-600 score lenders.
If you'd like more help with this and want to apply just give me a call. I'll be around this weekend and my telephone applications take about 15 minutes on average.
To see my blog post on how lenders play with your interest rate check out Spokane Homes Blog.
My office line is 509-252-9151 and I'm right her in Spokane. - Sat Sep 12 2009, 12:44