how can i get money for my cap room

i need 70m or more to sing a player i made he is asking for 66m but i only got -18m how i get money

Various in-depth tips and guides have been posted several times, I'd recommend running a search for them here in the NBA Live 08 Dynasty section. Very basically however, you need to either stockpile expiring contracts by trading your players for players whose contracts run out at the end of the season and then getting the cap room at the end of the year or if you want cap room right away, make trades with teams who do have cap space and exchange big contracts for small ones.

You'll probably want to do the latter but it won't be easy as you'll need to cut that $18 mil off the payroll to get even then clear up enough room to cover the first year of the contract you're offering without going back over the cap.