Mates Rates now theres a minfield.
The best way is work out how long the job will take, Then charge x pounds per day,Pro Decs will be charging 120-160 a day.
Now depending how good a friend your mate is will depend how much you knock off your rate for a days work.
Also try to find out how...
A health and safety policy is a declaration the you will to the best of your abilty look after the health and safety of you, your employees, the public and all other people you come in contact with while carrying out your work.
Even if you are a one man band you still have responsibilities to...
There are many types of wood filler on the market a trip to your local decorater centre may be a good idea and perhaps take a off-cut of the you have used and match the colour you need.
They normally come in small 250ml pots might be a good idea to purchase the two closest colours and mix...
Ready mixed fillers are crap should use a branded powder filler you mix yourself
As for priming just use some of the silk emulsion you are going to put on the walls over the filled patches, but make sure you thin this slightly with water.