The market allows you to pick and choose the jobs you want to do. Many jobs have flexible ranges in which you can complete them. For these flexible jobs, when you see a job you want to do you can accept it and schedule which day you will complete it.
Some jobs allow you to have more than one job of the same type in your basket at the same time. This will normally include a maximum allowance and it is always important to check the timer associated with each job to make sure you have time to complete them all in the given time. Please don't hold on to more jobs than you can complete.