[Demisis_P2P]

Just make it a flat rate $5 per kill.
As long as it takes more than 8 seconds to walk from a hospital bed to the hospital door then there won't be any point laming kills for money, since $5 every 8 seconds = $37.5 per minute and most other jobs pay about $40 per minute anyway.
No special anti-laming protection or anything needed, just $5 per kill. It would almost literally be one line of code to add, because the money a player drops when they die is calculated based on their K/D already. A player with 1000 deaths and 1 kill will drop much less money than a player with 1000 kills and 1 death. Which is why back in the day Blookat had his deaths set to 1000000000 and used to walk around with all his cash on him. You'd just need to change that formula to "5 + (whatever is already there)".