I have 450 sq ft that's on the ground floor. Like almost 0 elevation at all from street level. 100 year old building. I live a 10 minutes walk away from the Pacific Coast, SF climate
Every time I wake up and go to the bathroom, I see 2-5 insects in it. 1-2 are cockroaches, rest are some other small thing. Flies maybe? Always see some cockroach droppings on sink counter that I have to spray and wipe down
Every time I leave a room dark for a few hours and turn on the lights, I always see 1-3 insects
During the day with lights on, I notice 1-4 insects per hour in various places excluding tiny fruit flies. Those I probably see like 5 times a day
Problem has been getting worse since I've moved in but this is also the first summer I've lived through in this place
And if I need pest control, how much work is it to have them come in? Should I just move apartments if I need them?
I would get some boric acid (borax if you can't get your hands on boric acid).
Mix peanut butter with powdered sugar and boric acid. Idk the exact quantities but there's info online. Place this into small dishes like the lids of bottles. If you have pets or small children who can access this stuff, try using small metal containers like mint tins with small holes in them instead in order to keep them safer.
Distribute the peanut butter mixture into corners and crevices. Under the couch, behind the fridge, beside the oven. That sort of thing. Try to put them near where you see the insects most and around any areas where you do food prep or have food waste.
The peanut butter will attract most insects because it's high in protein and it's oily. Adding sugar will attract insects that are attracted to sweet food, such as certain types of ant. The bait won't dry out and it won't go mouldy unless it gets wet.
If you have a particular spot that is a problem, consider leaving diatomaceous earth in that area. DE needs a little bit of caution and you have to handle it approximately so it's not necessarily suitable for all applications especially if you have kids or pets. Check info online if you intend to use DE.
For the small flies it's going to depend on what type they are. Drain flies are common around wet areas and they are just a nuisance but nothing to be overly concerned about. Cleaning your drains should mostly address this. Other flies like fruit flies and vinegar flies are attracted to food waste and getting rid of them requires removing food waste, keeping fresh fruit in the fridge while you deal with an infestation, and keeping your trash and compost bins covered while remembering to empty them frequently.
You can make simple traps for fruit flies and vinegar flies by putting some fruit juice like apple juice into a wide, shallow dish and mixing a drop or two of dishwashing liquid into it. The dishwashing liquid is a surfactant that changes the surface tension of the liquid so any flies that touch it will end up sinking and drowning themselves. You can get more elaborate with a trap like this or you can use vinegar (especially wine vinegar or apple cider vinegar) to target vinegar flies specifically.
You can also make or buy little inverted cones to put into the neck of a bottle which has some of the above to lure in flies but preventing them from escaping. A small funnel will probably work just as well. This will make the trap much less prone to drying out and it will be better as a sort of preventative measure or a longer term measure once the initial infestation has been dealt a solid blow.
Most pest control amounts to taking these steps to prevent/manage infestations. They use different chemicals and stuff but they will probably do essentially the same thing. If you have a major infestation like where you have cockroaches coming from the walls then you need pest control because a few traps and being more diligent with food waste isn't going to fix the problem but most minor-moderate infestations can be fixed with DIY solutions, which it sounds like your situation.