If you're asking this question, the answer is probably NOW . A demo is good to have from the start. This way you always have something to present to people who are interested in what you're doing and they something they can share with others who might also be interested. And, if the quality is good enough, you can sell your music to your audiences and help support your mission. This is a major step and should be taken seriously.
Recording is a very involved process, and there are several factors to consider.
Define your goals and make sure that your project is on track with the goals you set. Don't be shocked by production prices. Studio rates vary quite a bit by geographical region, equipment, services, etc. You should be able to find a reputable production company that offers packages for a couple of hundred dollars per song. Get demos of their previous work and even references to make sure they can deliver what they promise in a quality demo recording.