The state has preemption for firearms laws, meaning no local municipality may enact and enforce stricter firearms laws than the state laws. A notarized signature is not a state law nor is the ability for a municipality to charge for the notary.
That said, I’ve never purchased a pistol without a CPL as obtaining my CPL was the first thing I did when I turned 21. With a CPL, for an estate transfer, the executor and beneficiary would fill out the RI-060 as seller and buyer respectively. In this case, without a CPL, the beneficiary will need to obtain an RI-010 License to Purchase from the local LE department. See MCL 28.422 section 8.
No where in MCL 28.422 does it state a notarized signatue is required on the RI-010. In fact, section 5 lays out a maximum $1 fee for providing a copy of information entered into the registry database. Therefore, without a fee explicitly stated in this statute, there cannot be a fee charged.