I agree. I started my own company after I was 50, only I deliberately left corporate employment to do it. There are lots of small businesses out there that need IT support and custom coding. Build your system admin chops. But you also need to be prepared to build your business (and yes, You have to build it. No matter what President Obama might have said, nobody else is going to make it happen.
Plan on working without pay at first. No, you don't have to provide free services to customers. But you have to let the money that comes in go back to the business to build it. You can't plant a seed, then yank the first green shoot that comes out of the ground and eat it. You have to nurture it and grow it. Your business has to build and grow so you need to invest your time and re-invest the money that comes in. When I started my company, I committed to two years without pay. I had plenty of savings from 15 years of corporate employment as a systems engineer and a spouse who had a job with benefits, so I could afford to do so.
Read _The E-Myth Revisited_ by Michael Gerber. This will help to prepare you for the business side of business - if you already have excellent tech skills, your business will succeed or fail based on how well you run the business side of things.
You must build a marketing plan. No matter how good your tech chops are, no matter how excellent your services or products may be, if you don't have customers you have no business. Identify some vertical markets you can target. Perhaps there is a single vertical product you can sell - Medical office practice management systems, or Sheep herding management systems. I don't know what you do, but if you can find an industry vertical, identify consortia and trade organizations in that vertical, find member businesses, speak at organizational events, become a thought leader for that vertical. If you're a generalist, fine, but if you can identify some vertical markets it will be helpful, and market, market, market your services.
As a programmer you should be able to understand this: A program is a machine (a code machine, but still a machine) that is designed to automate a task or set of tasks. Your company ultimately is a machine designed to automate the earning of money. Design your business with the goal of ultimately running without you. Learn to outgrow the employee mentality you had in the corporate world, and be a business owner. Build your business, create jobs, then once it's up and running, you can keep your hand in the business but it will not require you 24X7. Your employees will run the business.
It will be much tougher than showing up for work in the corporate world. Your only employee review is your balance sheet. If you can make half the money you made in the corporate world (after taxes and expenses) congratulations - you have a running business. If you get it running on all cylinders and get it to replace your corporate income and then some, then BIG congratulations: you are an entrepreneur and job creator. And you have created a business that will provide for you and your family. Design it with an exit strategy in mind: build it to a level of recurring revenue and sell out to a larger competitor when your valuation is enough to provide for your retirement, or build the business enough to create the cashflow you need (personal cashflow after the business is taken care of) and keep an office as a place you can go putter as you keep an eye on things.
It will be the toughest thing you've ever done, even if you're an ex-Marine. But it can be done. Those who can cut it never look back. If you fail, at least you tried.