He's probably going to gain money and get the clothes while he does the mission, like if he's robbing a bank, then he'll have to wear suitable clothes for it. Or, he could just buy the clothes from the shops, don't know if this feature has been confirmed.
Nearly everyone here knew that. You're wrong, it doesen't give you $25,000, it gives you $250,000.
I have maxed out money in San Andreas and in Vice City except for GTA III, I have like $500,000.
That AK-47 that Niko's holding looks so realistic, Chinatown has definitely improved. The clothes that he's wearing look like it's from Kane & Lynch: Dead Men.