Although I'm one of the more "senior" members of this forum I got into karting about 4 years ago as a way of keeping myself as sharp as possible for as long as I can - growing old disgracefully.
I'd been going The Ring on an annual basis for a number of years and did a few track days in the UK and I thought karting would be a good and relatively cheap way of getting my "fix" on a regular basis throughout the year. I started off with a friend doing Arrive & Drive in Pro-Karts at a local track and after about 12 months I decided to buy an old Rotax Max with a trailer and spares as a complete outfit from someone local selling on ebay. My most local track (over 40 miles away) does Practice Sessions twice a week and being retired, I'm able to go whenever the mood takes me. The difference between a Pro Kart (2x GX160 engines) and Rotax Max (2-stroke) is quite a jump and great fun.
2 years ago, I bought a Rotax DD2 (paddle shift gears, with front and rear brakes) which is faster again than the Rotax Max with unbelievable stopping power! I generally take that to practice days at Whilton Mill International circuit (near Daventry) where I get over 70mph out of it.
My B-I-L held his company's Endurance Karting meet for his client's at Buckmore Park 3 years ago which I'd never driven before and drove their Sodi karts. Out of 100 participants, I was 1/10th second off the fastest time of the day which driven by someone who was at least 2 stones lighter than me and my lap times were ultra consistent. Proof that regular practice in a kart does work.
If I were younger, I'd definitely want to race, but I just enjoy doing the practice sessions and all the spannering and tinkering with the karts back home. Getting the best out of the karts in different conditions is very technical and I find it an absorbing hobby. Racing can be extremely expensive (£120 a set of tyres for one meeting etc.) but the way that I do it is pretty cheap (buy discarded sets of tyres for about £15 and run them until they're worn out) and you can have a lot of fun from a gallon of petrol.
N.B. If you get into karting seriously, make sure that you always wear a rib protector otherwise you'll damage your ribs (ask me how I know?)