All snakes are difrent. You can't put an age or size on it to be exact. Just because a 14 year old human may be able to reproduce doesn't mean they should be. Don't take this wrong but you should really narrow down what you want to breed and research that. Saying some huge list of snakes tells us you are interested in breeding and thats great, but please do some research before asking such a question. Also, before you breed think about the following
-will you be able to feed 20+ snakes at one time(most of the snakes listed will make that many)
-Clean up after 20+ babies
-Properly house(perferably seperately) 20+ babies at proper temps and humidity at the same time?

Red tails of any kind are becoming more and more popular all the time for many reasons. The market is exanding and in that it makes it harder and harder to sell baby boas. The same thing as been happening to burms over the years until we are at a point like now where burms are available for under $100 and they are sold day after day in pet shops that don't educate people that buy them then later dump them off in the wild or some shelter

Sorry, I felt like clearing out my system