What kind of loans are in this portfolio--consumer mortgage loans, only?
Obviously, you would use docusign (or a similar software product or service) to transmit the documents (notes, D/T's, other contract documents, and federal disclosures) to be signed or acknowledged. As Randy advises, that means you must be ESIGN compliant for delivery of the federal disclosures and UETA or ESIGN compliant for delivery of the contract documents. Before accepting any of these documents at face value, potential investors will have to approve the way you handled the consumer's consent and e-delivery of the e-documents.
The law recognizes digital signatures, but sets no clear standards for validity. That leaves the holder of the digital agreements/disclosures/signatures at risk of consumer repudiation. A judge, jury, or expert witness can apply the eyeball test and declare a wet signature valid or forged. It will be up to the holder of the paper to make that case when the signatures are digital.
If I'm an investor, why do I want to take these risks if I can simply refuse to accept anything but paper and wet signatures?