Guy no1: Invites to player match
now who ever was the host of the player match switches it to a private match then a combat training then the host backs out of lobby
Guy no2: Should get an error just click A on the error and inv guy no1 back when he joins switch too a wager match then a player match
Guy no1: you should have a screan saying "The match is now about it begin and underneath your gamertag it should be matched player then now you back out
guy no2: stay in the lobby dont do anything at this time in moment
Guy no1: Goes too a Private Match changes map to Nuketown, switch the game mode to Search & Destroy and Edit Game Options (At this time dont touch the time limit just change the lives to unlimited) after you changed it to unlimited DONT TOUCH ANYTHING STAY AT UNLIMITED LIVES when guy no2 sends u an inv dont press anything just press your green xbox button and accept Guy no2's invite from their.
Guy no1: Once you are in there you should still have the option to change the lives dont change anything just press B.
Guy no2: After all that you back out to make Guy no1 host so the rules change to Unlimited Lives now u join back to guy no1s game

FINISHED

Note this may not start because you either have;

Not enough players in the game (Sometimes 5 is minimum)
It goes black after starting

If it doesnt work just PM me and i will do my best to help you

Please + rep if it worked for u guys.

THANKS!