I learned this from my mother and I have not seen any roaches in my house since. I sprinkle Powdered Boric Acid along the backsides of my cabinets and closets. Also another tip, if you place moth balls in your flowerbeds outside and in your garage this will deter snakes from entering. You can get both of these products from Home Depot.
Oh yeah! One thing I forgot to add, although boric acid is considered to be a pesticide, it is in my opinion Far Less Toxic than the over the counter brands. And I have 2 dogs and 1 rabbit that live in the house and they have had no problems.
For the fast-kill when you see one, I keep a bottle of isoproyl alcohol handy... It's cheap, it works, and disinfects the area at the same time! Just splash it on them... Soak em. If they run into a crack, under a baseboard, etc... I just splash it in there... It makes them come running back out again where you can step on them, or splash em again. They'll flip over once wet enough, and die, but I typically squish em if I can just to make sure.
(You just need to air out the room after doing this. Don't stay in breathing the alcohol fumes too long.)
You don't need much money but it will take quite a bit of work. Clean your house until it shines, especially in areas where food is stored or prepared. Clean up behind and under the stove and refrigerator. Roaches are looking for a free meal, don't give them one. Forbid anyone from eating anywhere in the house except for the kitchen and dining room and then make sure they clean up the table and rinse off dishes. At the hardware store you should be able to buy boric acid powder. This is a natural and safe way to kill all types of bugs - it causes cracks in their shells and makes them dry up. You can also use something called "diatomaceous earth" (DE for short) that is available at swimming pool supply stores. Sprinkle small amounts of one of these behind appliances and along the baseboards in the kitchen.
This works as a Bug killer, cleaner, Disinfectant and degrease. If you mix 1/2 cup white vinegar, 1/2 cup powder borax and two table spoons Simple Green (optional) in 32 ounces of hottttttttttt water (to dissolve the borax powder) once the powder dissolves it's ready to go. We have used this for ever and I just recently found out that it kills roaches and ants also. I added the simple green to cover the smell of vinegar.
