All I have for pest are bugs and spiders . . .
That broadens your choice of chemicals. My primary target is scorpions and there are only a couple of chemicals that are effective on them. I use CY-Kick CS and I know it's effective on scorpions as well as on other 6 and 8 legged creatures.
I used to pay $69 a month for this guy to spray. However, we'd still see scorpions inside the house. He used a different chemical, Demand CS, but I don't think it was the chemical that was ineffective; it was his technique. He'd show up with his sprayer then apply the chemical around the external doors, and inside the house where I reported seeing the bugs.
The bugs didn't just get in through the outside doors. They climbed up the walls, into the attic, then dropped out of the light fixtures. My previous pest control guy claimed that scorpions can fit through a thin crack barely big enough to slide a credit card through.
I bought an inexpensive sprayer (on sale), bought the CY-Kick CS online, then started spraying the recommended concentration around the entire perimeter, on three feet of ground and 2 feet along the wall. I knew that there were scorpions already in the attic and we saw a couple of them inside the house over the next 3 weeks. However, none have shown up since. I only do it once every quarter.
Make sure you use protection such as gloves, mask or respirator, etc. The guy that used to spray here didn't have any protection at all, and he was weird. Spray on windless days, or always stay upwind. Some of these chemicals, even in trace amounts, are also lethal to pollinators such as bees.
