No he can't. If Bernie has any money left over then there are four things he can do with it. 1) He can give the money to charity so long as he personally doesn't benefit from it. 2) He can give to individual candidates up to the maximum of $2800. 3) He can give it all to state, local, or national political party committees. 4) He can roll it into a future political campaign, i.e. Sanders for Senate 2024 or Sanders for President 2024. He can't keep any of it even if he paid taxes on it. That perk was outlawed years ago.
He can form a PAC and put a figure head in charge and then hire his family members and friends at inflated salaries.
Can’t he buy copies of his own book and then give them away still getting the royalties? I think this is how he paid for his houses.