You are never too old to be karting. The United States has drivers older than 60 and even 70 years old still racing. Karting, as a sport, is a hobby for about 95% of the people involved. The other do it as a profession, or as a building block toward professional motorsports.
Success in karting will not happen overnight. It takes hard work and determination, just like anything else. If you don’t have the funding, I would stick with ‘Arrive & Drive’ until you can afford to purchase your own kart to race competitively.