The proper procedure for what has been described by most of the folks here is to use a tag line to a surface tender. A buddy team will not make a low or zero visability dive that much safer or even better. Unless you and the buddy you found have done diving in silty conditions, he might just make the conditions worse for you.
Your surface tender should know a set of line pull signals so you can communicate to some extent. I reccomend you reference the U.S. Navy Diving Manual
U.S. Navy Diving Manual or
SEA 00C3 Diving Publications and Technical Documentation for line pull signals. The line is a "lifeline" make sure you use a rope that is strong enough to haul you up and possable out of the water with. Don't use natural fiber rope, or anything under 3/8". 1/2" polypropalene work really good and it floats, so it will stal out of the way, most of the time. The surface tender also needs to maintain slight tension to feel you movement/signals and keep any excess line out of your way.
As a commercial diver, we are required to have a minimum of three people on a dive team. Two are required to remove a diver from the water if there is any problem and the diver is incapacitated. Have a plan if you are injured: where is the hospital?, how do you call EMS?, is there a ladder for access or is there is sloping shore line at the end of the slip?, how is the surface team going to get the diver out of the water?
If this guy is offering you any reward, or compensation, you are now a commercial diver and you must follow the OSHA rules for diving work. Otherwise you can be fined, if you get hurt your insurance company may tell you to pound sand and the guy that has hired you is liable as well. Think about it.