Nope. While the vast majority of second round picks do end up with guaranteed contracts, there is no rule that makes it so. They are essentially restricted to negotiate with the team that owns their draft rights. If that team has no cap space, roster space, and has used both of their 2 way exceptions, you could be out of luck and have to accept a G league assignment (pays about $35k) That’s part of the reason you see 2nd round picks thrown into trades seemingly indiscriminately. Some teams literally can’t sign them.