[Alessio]

You'd be paying for your first few seasons with your fingers crossed that results and luck go your way enough to attract some sponsors/financiers who can help subsidise some of the costs.

The best way to go about it would be to contact some teams in an entry level series, something like Formula Vee or touring cars, and work out a budget for the season. Realistically, without money and a long-term karting background it's going to be hard to make it without a lot of luck.

An alternative would be to go down the karting route. Buy or rent an X30 kart, build up some experience and race in the nationals. It's not quite F1 or WEC and there are few 'paid drives' but the top level in national/international karting is nearly as 'professional'.

Honestly, though, unless you are willing to spend a lot of money, I'd suggest buying a kart and racing locally for fun as a hobby sport.