I'm sorry for your loss. I'm hoping your husband left you some money from life insurance. If he did, DO NOT use it for buying a house. Keep that to live on.
When buying a house, a co-signer is only used for increasing your ability to borrow more money or to have assets for down payment. It will not help you to buy a house if your credit is bad. You have to qualify on your own.
I would recommend a lease purchase to give yourself time to fix up your credit. This allows you to lock in your sales price now in case prices go up (if Obamacare goes into effect, housing prices will drop due to unemployment from closed businesses unable to pay for health coverage).
Other options may include private money, though the rate is twice as high and it costs more out of pocket.