Hi microvirus, You're never too old. Heck, with all your schooling, you should be able to start your own small computer repair business. However, with that said, you may lack experience, so that is what you want to work on the most, while you are still working.
You live in a large metro area, so I am sure their are very good possibilities for you. My own suggestion, to you, would be, to go on eBay, and find some cheap parts, for an entire system, to put together, and troubleshoot. You don't really need the greatest system, to start, just a PIII, or a socket 462 Athlon, running win98SE to start with. There are still a lot of people who run win98, so don't think you are cheating yourself.
Don't worry about the internet, at first, refrain from connecting to the internet, until you are familiar with the hardware and basic software of your system. Learn the file structure (Windows Explorer), and become familiar with the main folders and the files contained in them. Click on all the .exe files you find, so you know what they are, and where they are located.
Practice tearing apart, and putting your practice computer back together. It takes me about 5 minutes, to strip any one of my computers down to nothing, and about 30 minutes to put them back together. Putting them back together is where you learn to troubleshoot....lol, you'd be surprised if you forget one thing, how it can lead to other discoveries.
Most important, look at this as a hobby, you'll be surprised at the rush you get when that first system fires up, and everything runs, and you'll get that same rush with every system that you put together. Practice makes perfect, they say, but getting over the fear of damaging the computer, is something many people have a hard time getting over.
If you have friends, who own computers that have problems, offer your assistance, to help them. You could post a small ad at a local grocery store's bulletin board, to start your business. You don't want to get to much business, at first, until you are comfortable with what you are doing.
You don't want to charge a lot of money either, until you know, that you can deliver quality service in a reasonable time. If your customer is satisfied, with your work, they will tell others. However, if they are displeased with your service, they will tell others more than once....lol. Once you are well established, and have proven quality service, then think about charging more, but keep your prices below your closest competitor.
Look for service ideas, like I go and pick up my customer's box, for them, and work on it at my home. That way the customer does not have to sit and wait for you to work on it at their home, and plus you have all your tools at your house, so you both win. Keep your customer informed, as to what problems you find, and an estimate time that you will finish, and return their computer. Also, don't replace any hardware, without the customer's knowledge, if you find something bad, let them know, right away that it's bad, and how much the part will cost; you can add a slight markup, but don't go crazy. I always buy cheap memory, on eBay, just incase the customer doesn't want to pay the higher price, for new memory, I offer the used memory as an alternative. I've had pretty good luck buying memory off eBay, as all my machines have memory, from there, in some form, or the other.
Repairing computers, and seeing the happy faces, of your customers, is a gratifying experience. Of course, I live in a small town, out in the middle of nowhere, so I am sure you can make a good go, of your own computer repair business, just be honest with your customers, and you will succeed.
That's advice from one 50 year old to another. I never intended to repair computers, I just fell into it, when somebody asked me, to look at their computer, to see if I could fix it. Well, after that, I was getting a lot of calls, and they haven't let up yet. Good luck and best wishes!