How much do the Avengers get paid, the actual in-universe characters?
A quick Google search for "how much do the avengers make" pulls up Webpages on how much the actors make.
While the actor's earnings make good reading, there also is a bit more info to be found out there.
How much then do they get in regular money? This is never disclosed so in the realm of pure speculation. Assessments range from 59 (US FBI agent entry level) to 120K per year. These are mainly based on the characteristics of S.H.I.E.L.D. as an agency of the US.
What are the salary and perks of Captain America?
I remember in an old issue of Avengers when Spider Man helped them out and was considered for membership he was thinking how the thousand a week salary would really come in handy.
This was back in the late 80's or early 90's so I am sure by now it has come up. I think it was mentioned that there was a Foundation set up in the name of Tony Starks parents that paid for the Avengers, their mansion, tech and their salaries. The money for the Avengers couldn't be touched by Tony or his company so when he lost his company and went broke the Avengers were still funded.