What if: sugar baby!shouta & sugar daddy!izuku
Still an age difference and shouta is the older one
But izuku is an adult & doesnt have many friends (he has a small few tho) or much of a sex/social life, and when his friends signed him up for a sugar site as a joke, he went along with it cause he's got money and he likes using it to make people happy
(he already donates a ton, but his government-adjacent hero analysis & quirk consultation jobs pay really well, and his parents invested their money early and it blossomed massively so theyve never wanted for anything tho izuku and his mom lived modestly. So he's got a lot of money and nowhere for it to go and if he can get a fuckbuddy/datemate out of it for relatively pennies, then why not? It makes him feel useful and helpful and also gets him something of a friend)
Shouta, as an unknown underground hero and also a teacher, doesnt get much in the way of money. UA pays a basic living wage, but different expenses (medical, insurance, costume re-makes, etc etc) arent always fully covered by hero insurance, so he tends to live simply and never really have time or money to go for the good things in life. Including a social life. Hes a gay transman with no time to flirt and very little actual flirting ability. So he does the sugar baby thing as a sort of supplement - he gets sex and spending money and no strings attached or long term commitments.
The two of them meet up and dont immediately see eye to eye (shouta is not quite used to being spoiled the way izuku wants to, with gifts and items and covering costs for things just bc he can) but they enjoy the sex and keep meeting up until they're intimate friends.
Shouta ends up revealing he's a hero & izuku tells him he already knew. Izuku keeps his quirkless status a secret for as long as he can (for fear that it will make shouta leave, disgusted) but it does eventually come out.
One of Izuku's friends is Hitoshi who may or may not have some separate connection to aizawa/eraserhead [but i havent explored that yet]