I had huge ants infestation in one of my homes and the over the counter poisons were garbage.
The "2 years protection" poison would kill ant that were directly sprayed, but 20 minutes later new ants walk over it.
For good poison you need to have licence, or hire licences guy.
That said, I discovered the same thing homedad did.
Ants don't live in the house - they live in nests in the yard and come to the house for feeding.
Meaning if you park the motorhome elsewhere, they will be gone.
Can't officially recommend poison that work well on in-ground nest, but gasoline is way cheaper than the cheapest poison you can buy.