The big thing is the mattress so that guests are really comfy since an office is not an ideal guest room you want that bed to be awesome.

Check out The Sofa Bed Store, you'll get a great mattress and they come apart to fit up stairs. Avoid Ikea if you want it to be comfortable and last, go with Ikea if you need something temporary in my opinion (when in budget of course). I have their most compact model and it arrived in a few boxes, wasn't horrible to assemble (and this meant I could choose what would fit the room, not what would fit my condo's elevator!) I have the Stretch, but they have others that will fit https://www.usa.thesofabedstore.com/collections/the-entire-line-up