You are welcome! I've learned much of what I know the hard way... it's nice to be able to help folks out and maybe give them a bit of a short cut!
Fleas are... funny. We had major flea problems for years... house cat or two, barn cats, dogs... For some reason, for four years (2015-2018) we didn't see a single flea! Even the barn kittens- which are absolute flea magnets- were completely clean. Oddly, 2016 was the worst TICK year I've ever seen. Our dogs weren't bothered, but the neighbors had dogs whose entire heads were covered by hundreds of the rotten things. And I saw my first (and thankfully only) case of "tick paralysis" that year in a dog.
I really dislike using chemicals on animals, but ticks carry way too much disease, and fleas cause intense discomfort- we had an Australian Shepherd/Blue Heeler mix who was so allergic to flea bites that ONE flea would cause her to itch and scratch and rub on walls and anything else until she was bald and raw in spots. And once they get entrenched in the house and lawns... they're a giant pain to eradicate.
I use the "spot on" type products as sparingly as possible, and we don't have carpets, which is a huge help. For non-chemical control, you could try sprinkling diatomaceous earth along the edges where the walls meet the floor, and in areas where the pets spend a lot of time. There are also water traps... you plug a small light (warmth and light) into an outlet near the floor, and place a pan of water with a bit of dish detergent (to reduce the surface tension... without it, they'll just hop back off the surface of the water!) The fleas are attracted to the light and warmth at night, and land in the water and drown.
Of course, around here, Maggie- the VERY curious and active Border Collie pup- would drink the water, or pick up the container and dump it everywhere. Sigh...
Summerthyme