Have the current medical to apply and most companies will require it to be current to interview. Some will require it to be current when you show up for the first day. Some require a Class 1 to be current (within 6 months) and some a Class 1 within the past year...depends on the individual company requirements. Some companies require a "company physical" to get hired. Others chose to eliminate the company physical and require the current FAA physical instead to save money. I'd take the FAA physical over the more detailed company physical any day.