You can do as many or as few as you like. If you want to go to the national championship runoffs, which you should at least once if you're doing wheel to wheel because it's an awesome event and you'll face the best drivers in amateur motorsport and find out if you suck or not, you need to do three race weekends plus the runoffs week. There are always enough events out West to cover most of the season if you want to be on track a lot.
SRF (SRF3, really, that's the one you want with the updated 1.6 ford motor) has the benefit of the CSR network. These are businesses dedicated to supporting this particular car at the track and away from the track, and are able to provide anything from parts and pieces if you do your own work on your own car through full service arrive-and-drive cars to rent. There's usually one at most SCCA race weekends.
I am capable of maintaining my car myself and do, when I need to, but I often take advantage of the CSR as it's a built-in crew to take temps and pressures, help with setup changes and string the car, make sure everything's torqued and fueled properly etc. Since I own my car and manage my own tires etc., it's only a small upcharge beyond the entry fee if you bring the car to the track. Many CSR'[s also store and maintain driver-owned cars and transport them to let people loose from the burden of trailer and truck ownership. It can be a great setup for a gentleman racer who doesn't want to race wallets with the next gentleman, because the cars are really really really close. Whether things go well in a race or not is entirely up to the driver. They don't break much and contact usually doesn't break a car either. There is a huge amount of crash structure between you and the other cars as well for a small open car, the entire side pod on both side is just open space.
Even though it's an open cockpit car (meaning you must use arm restraints), the cockpit is so spacious that it's easy to learn how to get yourself strapped in without help unlike some formula cars that make it really hard to do on your own. Has a starter, synchros, reverse, uses cheap long-lasting Hoosier spec tires, brakes can last a season...it's a good train. And the racing is GREAT. The cars do comparable times to what a stock-motor, with suspension and race tires E92M will do around most tracks. Imagine that kind of pace, in a pack of 25 cars nose to tail, butt 4" off the ground in an MR open car that drives mostly like a 1600lb boxster, sorta. It's pretty awesome.
Highly recommend setting up a drive, if you're interested at all, with one of the CSR's. An arrive-and-drive weekend is usually $2-4k depends on the entry fees and the rental place. If you take the rental out of the equation, and own the car, a race weekend is $400-700 for entry fees for four sessions (two qualis, two 30-45 minute sprint races) plus 1/3 of a set of the $800 tires, plus gas (7-10 gallons depending on the track, more time spent on a straight means more fuel per hour, winding tracks less). So, figure like, $1500-ish not including stuff you tear up. Bodywork is cheap to fix, it's just fiberglass. The suspension is easy to fix, it all bolts together and has sacrificial arms and heims. Even the frame is relatively fixable, it's just a bunch of square tubing welded together. The only expensive thing you can really do is blow a motor ($5k + labor and other bits like oil cooler if it blows badly enough), which is rare and usually involves a money shift and/or crimping the nose closed hitting something and then overheating the car after ignoring the dashboard for laps.
https://www.scca-e.com/ has a list of CSR's.
Aw - Clay Russell is on the front page right now for his Runoffs championship last year. He beat me by a nose one time (with another driver pushing him up the hill at Road America, bastard), now I get to pretend I almost won the Runoffs by the transitive property of racecar drivers