Just to let you know, throughout the process there may be multiple occasions when you will be asked to provide sensitive and personal information of all sorts, including how you live, how your intimate life is, finances and many more. USCIS can in some cases even visit your place. So if you're not ready for this, I'd think twice before sponsoring somebody. The expectation is you're very transparent with agency about everything, and will eventually comingle finances or share other things with your future spouse and provide proof of that