Can I use SALT to Invest as I used to do it at btcjam, lendinclub, btcpop and other lending platforms?
Or there is no use as an Investor, and only as a Borrower?
Lending on Salt is not P2P, restricted to accredited investors only and very regionally restricted for borrowers and lenders. You should look into other platforms like ELIX if you want to get that P2P feel.