Best lens/body combo for around $600-ish?

The Micro Four Thirds habit is a progressive disease, and once hooked, the addict cannot escape the clutches of his addiction.

If you are going to do this thing, then the best way to do it would be to go to a Best Buy or other large electronics store and purchase a brand new OMD M10 ii with it's 14-42 kit lens for $600.  It will have a warranty, that it likely won't need, and you'll be able to take it back to the store within a certain number of days, which you certainly won't do.

After the initial rush of having a pint sized DSLR quality camera in your jacket pocket, you'll wander off into purchasing new lenses for your new toy, and those will include adapter rings so you can shoot virtually every interchangeable camera lens on your Oly that's been made in the last eighty years. The M10 ii has the top of the line 5 way in camera body stabilization that allows you to plunk any lens on the camera and it's stabilized.

There are cheaper ways to become addicted, in the short run.

A good PL5 or PL6 body is about $200 and a good M10 or M5 body is only another hundred or so.  But they need lenses, and the 14-42 kit lens is about $150 new and $100 in excellent used condition.  And, if you go used, then you'll not have the latest and best camera body.

The OM 10 ii is available gray market from Asia for $400 for the body, and if you'd like a refurb from an American seller, those are near $500.  Might as well pay $600 for everything new in the box, and start shooting.