Should I be included in my grandsons mortgage?

You can be, but it depends on your goals. Being added to a mortgage makes you financially responsible for the loan, while being added to the deed makes you a co-owner. It can help him qualify, but it also ties your credit and liability to the property. Many families choose co-signing instead.

Depends if his income is high enough to buy something suitable for you and his family.

I would speak with a local Lender, they can often tell you which way would be more beneficial. And as the other answer indicates, there may be some things to consider.

That would be a better questions for a mortgage lender. They would be able to tell you how much of a house he qualifies to buy, and that can determine whether or not he should add you to the loan. Just know, there is a little bit of risk because both of you will be liable for making the payments, even if you no longer live together a couple years down the road.