How do you keep bodyguards in gta 4?

You may not be able to keep them forever but u do keep them until you arrange plans with a friend or on certain mission parts they will leave, and become good enough friends with Dwayne to unlock the option of calling backup. He sends you 2 ppl one with a handgun and the other with a micro smg. And they actually do damage instead of off them missions where it looks like Little Jacob is shooting for no reason lol. And u can use them for missions.