Hello and welcome!
One of my favorite online stores is
Balsa Machining. Bill has a huge selection of body tubes, nose cones, centering rings, balsa fin stock and blocks, etc. for the scratch-builder. His prices for motors are very competitive. And he has one of the lowest-priced mid-power kits available---the 3" 29mm 'School Rocket'. And a .
AC Supply sells discounted Estes kits and motors (you have to put the item in your cart to see the discounted price, because Estes). Great service.
JimZ's site has plans/instructions for most kits that Estes, Centuri et al have ever made, as well as "Design of the Month" rockets and many others.
OpenRocket is a free and fun program for designing rockets, testing for stability, estimating altitude, etc.
Here is a list of some OR files for older and current rockets. You can print templates for fins, transitions, nose cones, get altitude estimates, etc.
Eggtimer sells kits for altimeters, GPS, flight computers etc. Cris's kits are so inexpensive that some rocketeers buy a kit for each rocket. The
EZ-DD package includes a 3" rocket designed for dual deploy, and an electronics bay, altimeter and wiring, for just $100. It will fly on mid-power and can be used for L1 certificationa on any H or low-end I motor.
Warning: Rocketry is a bug that bites deep and rarely lets go.
It bit me around 1965...