? I am new sorry ?

There is no limit to how many you can have total, as long as your shop or showroom is large enough to hold them. You do have to pay to increase your Rancher shop/Showroom size. There is a limit to how many you can have on your Profile at once. I believe the limit for Merchants is 10, and the limit for Ranchers is 25 (It's been a while since I've checked so someone please correct me if I'm wrong).
I think the idea behind that had to do with training creatu, a feature we used to have back in the old days. Since Ranchers primarily make money selling creatu, they needed the extra space to have creatu out for training so they could increase their value. Training has been broken for some time now. There was talk about reviving that feature and possibly having creatu battles, but I'm not sure what the current status on that project is. Also, Ranchers can hatch 3 eggs per day, while Merchants can only hatch 1 per day, so that extra profile space gives Ranchers a little leeway for hatching.

Thank you!