1. If you are in transfer period, you can sell some
players you don't want and replace them with
cheaper and younger players
who would eventually grow to the same level
(I would recommend buying young&cheap
players from Brazilian league,
and give them the longest contract you can give
so wage doesn't increase during the years)
2. If you are not in transfer period,
I'm not sure if this works for Next Gen,
but renew players' contract to a cheaper one.
It should be easy with United
because they should have a good negotiator.
You need to pay a lot for renewing contracts,
but you can set the wage to about 1/2-3/4 of the original wage
and still the player can accept it.
If he doesn't accept the offer,
don't save, quit manager mode,
then come back to make a slightly better offer.
I'm sorry, the last part of the second idea might be cheating.
I think BraveTyger told you everything, so I just improved a bit of his answer.
