The trick is to accept that motorsports is not supposed to be easily afforded or something that can be done without substantial resources, and rally is the ultimate embodiment of this idea.
Once you embrace that, you then need to determine how to best maximize your financial resources and time and then determine what other things that consume those resources and how valuable they are.
If your under 25, put every ounce of time and energy into getting a great job that pays good money and only allocate rally resources to saving, volunteering at events, and crewing for teams so you can learn the true costs of competition.
The sweet spot for competing and participating in rally is 25-30/35 and then 45/50+, basically, when you should be able to have a good job/income without necessarily having things like family or house payment to consume your resources (time and or money). Then from 30/35 through mid to late 40s is time to focus on the career, family, house, and what not. Once that is all established, if you are fortunate enough to be able to generate enough resources (again, money, but also time), its time to get back to competing again.
If your 17 or 18, this isn't what you want to hear, but its the truth. So if your in that age bracket, get a dirt bike or a rallycross beater for your racing fix and work your butt off, either in school or in getting started on a career path (just because people talk about education, doesn't mean everyone needs a bachelors/masters degree to be happy, the world needs electricians and plumbers just as much as it needs an engineer these days, both career paths are capable of generating enough income to compete/have a good life for people that are driven) and if that career path includes education, do everything possible to graduate with as little debt as possible (you can't imagine how much it sucks to make good money but have half of each check going to student loans).
Once you have the job and the income, then figure out what you can afford and set your competition goals that way, maybe its a year of saving and then a year of competing, maybe its 1 local and 1 tow away race, maybe to make it big and its 5+ events a year.
But realize this is only ever going to be a hobby for 99.9% of people in the world, maybe you can get lucky enough and someone will someday subsidize some of the cost for you, but probably not, so figure out how to support yourself in the sport, work towards that, then worry about the car.