RE: Is there a limit in a day to the number of accounts I can sponsor in Hive SBI? How about sponsoring my wife and second son's accounts? Is this allowed?

Self-sponsoring has never been supported (a transaction memo specifying the account the transaction is from will cause the transaction to error in our system and no units will be granted until we can get in and manually assign the sponsee).

Sponsoring wife, family members, etc. is fine.

The answers to these questions (and more!) are available in our official documentation at https://docs.hivesbi.com