Not too complicated, a visit to a local FAA flight standards district office (FSDO) should enable your boyfriend to be issued an FAA private pilot certificate (VFR only). He will however then have to be "checked out" by the local FBO where you rent the aircraft, this will typically involve an hour of ground instruction followed by an hour or two of flight instruction so that the FBO can be sure that he is familiar with the local area and is competent to fly solo, this will probably cost in the region of $160 - $280 for your checkout plus the cost of the solo rentals, typically around $80 - $100 per flight hour. If this sounds a bit steep you may just want to rent the plane with an instructor ("Dual") for an hour or so, instructor rates are usually around $40 per hour.