You can go to an FFL and pay to do a transfer and have a NICS check done. Otherwise, the law imposes three criteria on the sale:
1) Resident of your state
2) Of legal age (21)
3) Not known to you to be a felon, or for you to suspect he is one
As a former resident, I do not recall Indiana imposing limits beyond the those federal laws, and I don't think anything has changed since then. So, you don't HAVE to do anything more. But if you want to, finding a dealer to do the transfer and paying for his services is the only way to go - they have access to the NICS system and the public does not. If you are looking to increase your comfort level, you could also ask him if he has a concealed license - if so, then he's clear. If not, ask him casually in conversation about other guns he owns, what range he shoots at, or what he thinks the best gun dealer is around your area, since you are looking for a new hi-cap 9mm (or something like that).