Don't waste much time with this person. You might end up requesting an ITIN for him and filing 1040 with schedule C. As soon as you tell him how much he will have to pay, he will walk away. The very first thing I do for these people is to run a quick estimate of their taxes and then I ask them, do you want me to start working on your taxes or no. If yes, I start the real work. If no, I wish them a nice day and call my next customer.
If you use line 7, the IRS will question the return sooner or later. Remember that you don't have all the information from the employer so the IRS will not know who to go after even if you use line 7 and treat him as an employee.