How many years of relevancy?
Classic albums?
Classic verses?
Hit records?
Grammys?
Certain amount of money?
Ability to tour after retirement?
Headlining festivals?
Influence and impact?

What would you say their bare minimum has to be?

staying relevant throughout different eras in one way or another

have music I enjoy

Honestly 3 great albums with at least one classic and you got a legendary run

Exception is if you die prematurely of course

Being able to create at least one record that can get women dancing in the club.

I'm being halfway serious halfway sarcastic.

tbh sarcasm and bullshit aside all the greats got one record that can turn a party out

hip hop was invented at a party and for party settings

even Em produced and rapped on Smack That

Be happy with the work

at least a couple good albums, maybe one Great one

getting to the popularity level that people recognize you by voice alone

Respect or atleast not getting Disrespect from rappers in your generation

at least be able to pop out at a few major festivals during your initial run

have a song or two that people can enjoy in a party environment

Getting to the point where you could realistically support your lifestyle with no other major income outside of music

Media outlets seek to interview you

Basically the opposite of what dababy going through right now

DaBaby is stamped already fam

even if he never has another Suge / Rockstar / Walker Texas Ranger level smash, he has more success than 90% of rappers that have ever touched a mic

you don’t have to like him or his music to acknowledge his achievements

Just because you’re not hot right now doesn’t mean you were never on

huneybuns

When it’s all said and done he gonna go down as one of the biggest jokes in rap, no rapper falls this hard and quick as he did

Who sold the most bundle$

Would be valid if he didn’t pop out with a viral hit months after.

nobody even remembers this s*** now f*** when it’s all said and done

Baby isn’t Suge level hot anymore , but he’s been doing well for himself recently.

Maintaining your core fanbase

It's pretty much covered in OP

If you're living off of making and performing music you're in the 0.1%