It's not a matter of being "good enough," if you do something that someone pays you to do, whether you're good at it or not, then you are a "pro" at whatever it is you'e being paid to do. There are "pro" athletes who aren't particularly good, there are teachers who aren't particularly good, there are lawyers that aren't particularly good, etc... but they're all "pros" at what they do.
If you build models for a living, if that's your profession, then you're a pro builder. But anything other than that... having some sort of honorary title of "pro" builder... is meaningless, because there's no measure or standard to identify someone as a "pro" builder. Anybody can call themselves a "pro" builder, and that's why the title is meaningless, unless you actually build models for a living, in which case you are technically a model building professional.