Every now and then you might see people talk about back-up bodies and lenses. Sometimes they'll have, say, an E-M1 II as their main body with an E-M5 II as their 'back-up' body. In Nikon terms, it's vaguely similar to having a D4s with a Df as a back-up (although I don't know enough about the Nikon system to make a true comparison). This makes no sense and I would say that it's bad practise. If your primary body malfunctions, it's certainly better to have the lesser camera than no camera at all. But an E-M5 is not a back-up to an E-M1. The only back-up to an E-M1 is another E-M1. The only back-up to a D4s is another D4s. The E-M5 is a complementary body. It's smaller and lighter than the E-M1 and it might make more sense to take it on a photowalk, or on a hike. So it makes sense to have one, but it certainly is not a back-up camera to an E-M1, anymore than a D3 is a back-up camera to a D4. You could have a Phase One system, plus an Olympus system (for example). The Olympus doesn't back-up the Phase One. It is there to do jobs that the Phase One is not suited for, such as birds in flight. It might be tempting to save some money and have a lesser camera as a back-up to your main camera. But I advise against it. Of course, there is the option to rent the equipment you need, and sometimes that works better than outright ownership. If your budget is tighter, the pay-as-you-go option would make a lot of sense.