Yes, your Warband character ages. Unfortunately he won't age more than three years before his stats start to drop, especially when being wounded in battle. Feature is not well implemented, since if you start at age 21, you're an old man by 24.
OK, the issue of shops (enterprises). Absolute best is making velvet in Rivacheg. Rivacheg is owned by Boyar Meriga at the start. He hates everybody and has a relation of -3 with you at the start. You must raise his opinion of you to at least zero or you cannot purchase an enterprise in Rivacheg. Easiest way is to ask him if he has a job for you. Ideally he will tell about sea raiders building a hideout in the area. Agree to eliminate the hideout, assuming your party is at least 15 men, then talk to him again. He will give you a reward and his relation rises to +1. Then 10,000 denar to the Guildmaster gets you a velvet manufactory in Rivacheg. One week after the purchase, it start making between 950 and 1,100 per week.
You don't have to supply it with anything, the person running the shop handles all that.