What do I need to do to get back into the flight seat
Legally, not much. With the recent third class medical reform you dont even need to get a medical. You will need to get a bi-annual flight review to get current as well as your takeoff/landing requirements for passenger carrying as per FAR 61.57. While your bi-annual only needs to be an hour of ground and an hour of flight, if its been 7 years it will be well worth your time (and possibly an insurance requirement) to spend some more time on both.
What are some good options for a 2 seat folding wing ultralight that
has a few hour range
Dont know much in this space so I wont comment
What are some hidden costs of owning a new or used ultralight
There is one guy on the field I fly out of who has one of the moving wing, snowmobile looking ultra lights. He keeps it in the back of another guys hanger and takes the wing off every time he stores it. With that in mind last time I spoke to him he said it takes some time to get the wing on and off and he needs to plan for that when he flys. If I remember correctly he bought his new or close to new and it was in the space of 75K which frankly is quite a bit considering you can get a really nice airplane for way less than that. The wing is fabric/composite so outside storage is a no go. You can hop around on nice days with it but its VFR only which depending on your goals can be a limiting factor.