Start the same way you would by being a foster parent, but tell them you are only interested in doing respite. It's a needed piece of every foster care experience, and they will work with you. You likely will still have to get a foster care license, and take all of the training required to do so, but in the end essentially are a babysitter for however much time you will commit.

I've always done my own IRA, it just seems better to keep it in my control. But there are other options.