We are glad you joined us, but please don't ask this kind of question; we would like to see you stick with us long enough to make your 1000th post.
Believe it or not, the cheapest way to go is to buy the commercially-made motors. If you want a price break, buy in bulk (like 500 at a time). There are some internet sites with pretty good prices, certainly better than many of the brick-n-mortar retail places.
It may sound like a simple thing to mix some chemicals, pack 'em in a tube, and light it. But it is far more complex than you realize.
Take for example the first step, making a motor casing. You are going to have to roll, press, cook (dry), and trim these things, and that requires LOTS of time. Then you will have to pressure test them to collect a database of structural characteristics; you will have to know how strong your cases are before you can begin designing a fuel grain. You will have to pressure test a bunch (like hundreds) to establish a repeatable manufacturing process, so you can assure yourself that you won't slip a weak motor case through the mill, load it with a standard propellant charge, and kill yourself (or someone else) when it blows up. Once you get things going, you will have to continue the pressure testing of sample motor cases to maintain quality levels.
Now consider the fun involved in designing a ceramic nozzle, building a machine to press the ceramic in place, doing more pressure testing, etc.
I'm not even gonna bother to discuss how complicated the fuel grain itself is.
You will have to develop a slow-burn pyro mixture to use for a delay charge. You will have to press a bunch of little 'pills' into motor tubes and do a bunch (on the order of hundreds) of test burns to understand the time relationships, and to assure that the delay will indeed ignite from the fuel grain, and will in turn successfully trigger an ejection charge.
You will have to determine how to size an ejection charge that will reliably kick out a chute but will stop short of blowing up the entire rocket.
You will have to run thousands of these motors through the test stand to establish the performance parameters of your new product----just for your own use. Because if you don't know what your motor will do, it will be of little use to you.
Repeat all this for the next motor design.
And overshadowing all this activity, which falls under the heading of storage, handling, and manufacturing of explosives, are all the city, county, state, and federal requirements. You will undoubtedly have to find enough land to be X hundred yards from any inhabited structure, and Farmer Jones is not going to let you set up a factory in his cornfield. You will have to obtain approved storage lockers for the chemicals unmixed, mixed, and for the loaded motors. As an amateur attempting this task, you will be uninsurable (and you can't try to sneak by the insurance companies by simply not telling them; when they find out what you are doing, any policy you have will be invalidated).
And keep in mind that the whole time you are doing this, you are risking your backside . . . and your frontside, your topside, your bottomside, etc. Things DO blow up from time to time, just check out what happened to AeroTech a few years ago.
Does this sound like fun? Not to me. Does this sound like you could save money? Not to me.
Sorry to lecture, but yours is a really really bad idea. Please accept this advice from someone who suffered hearing damage as a child and has lived more than 40 years since the damage, not being able to hear an entire spectrum. Your eyeballs, digits, and gonads are worth far more to you than their weight in gold, or anything else.
Stick with the factory-built stuff.
And come back soon with some easier questions?
