I have purchased a few affiliate accounts in this manner before.
You’d need to contact the affiliate program in question to check that they allow you to transfer ownership – any new owner will want conirmation of that (you only need to send them a very short email). Once you have got the payment, you can give the account logon details to the purchaser – who can change the payment info/contact info etc etc.
You’ll need to prove the monthly earnings – as mentioned above, confirming how many players attribute to the revenue will help a sale. Most affiliate programs will confirm the earnings, and give some kind of summary on where the revenue is coming from. If it is from 1 or 2 players, you’ll get less for the account than if it was 100 players…
As ChrisB said, guaranteeing the earnings can make it a better deal for the purchaser – but you just have to negotiate to a point where you are both happy. The purchaser might just prefer a lower purchase price…
I too think 6k is probably a bit optimistic given the current climate (a lot of people have solf off accounts over the last few years) – but there are buyers here on CAP (such as myself) if you decide to sell.
themac