I too have decided to make a career change into EMS at a late stage. I will be 43 in May. This will be my third, maybe fourth career
I wanted to do something tangible this time around... Kudos on your choice or at least thinking about making the change.
My story... I finished my EMT class in December, passed the NREMT in January and received my EMT and ambulance license in February. I am now taking Anatomy & Physiology and start Medic school in July. With all that, I second or third what other people have said... You will bring something that younger folks, for the most part, do not have. Life experience. I also found that I was a little more focused than other people. On the other side, it took me a while to get into the stride of being back at school and studying having not been in school for 20 years. I do owe a lot of my success to my wife, an emergency doc. She has been invaluable in her knowledge and her contacts.
In terms of schools be very selective. I went to a community college and was not impressed, though it was cheap. About $100... I did hear good things about another community college though so don't write them off, just talk to people about their experiences in your area.
I also follow on what people say about the money. I am lucky enough to have a wife to support us and what I make will be gravy. If you need to support your family as an EMT, it will be difficult. In the Bay Area, it would be impossible. Even as a Medic, the money isn't great and suggest if this is a concern to look at emergency department nursing. You will still be doing great things and making more money.
Also, as mentioned, if you are not in good shape, I would start getting there. This an area where age won't help you. If you're not in shape and start now, by the time you finish EMT school you'll be in a good place.
Happy to share any info or help in any way on your new journey. Congrats again and good luck!