Is there a program for elderly people on fixed income to have a house sprayed for bedbugs?

Not that I have ever heard of, no.
I would reach out to your local counsel on aging and see if they have any recommends.

Call the Health Dept in your County.

I haven’t heard of one, but I would find the website of your county’s Department of Health, and see if they have any information or recommendations. I do know my county was involved in some way in the abatement of bedbugs in an independent senior apartment building a family friend lived in. There were signs posted outside an affected unit.

Hope you find some help.