Look at the thread under "Picture framing business issues" that covers this same topic.
If you have an early retirement from a government job, that would mean you are getting as much now, or more, than you did while "working". If that is the case, then heck, go for it. It can be a hobby for extra money, may even turn into a business. As long as you honestly do not have to worry about income, picture framing is fun and relaxing. If it turns into a business, great, if not, have fun and enjoy it.
Will it matter to you that you will be able to set your prices much lower than the folks who have an established framing business in your neighborhood, even if they depend on it for their living?
If that is a concern to you, please consider looking for a location that will not affect someone else's livelihood. This will actually help you as well. You will not anger others in the trade, and that helps a lot when your starting. It pays to have friends in the industry.
John