Casper-
Good luck on the bidding... While I haven't had direct experience with the Edel cat, I have sailed on quite a number of catamarans and trimarans.
A couple of things about multihulls, you need to reef for the gusts, unlike a monohull, where you tend to reef for the average wind speeds and let the boat handle the gusts. You're much better reefing earlier than you would on a monohull, as the extreme stability of a catamaran puts much more strain on the rigging than a comparable size monohull could.
Watch the netting, it can fail pretty dangerously. If you have any doubts about its integrity or age, replace it.
Two books you may want to pick up if you haven't already. "Multihull Voyaging" by Thomas Firth Jones and "The Cruising Multihull" by Chris White.
I'd also take the opinions of people not familiar with multihulls about their seaworthiness with a grain of salt. A monohull often has to be built much heavier in construction, due to the inertia the amount of ballast it has gives it. A multihull, not having a heavy metal keel, often can be built lighter without sacrificing safety. Where monohulls tend to have to bash through the waves, multihulls tend to float on top of them. A multihull's light mass is often its best defense, as it will tend to move-instead of resisting a wave and getting crushed.
Things to watch out for on the Edel 35:
It has a partially cored hull IIRC, and you need to make sure that water hasn't gotten in and caused any delamination. I don't believe the core in the hull will rot as I believe it is PVC-based foam.
The cross beams that connect the hulls to the bridgedeck are aluminum.
Corrosion is going to be a problem at the fasteners, since I believe the fasteners are stainless steel. I personally prefer cats that have the hull molded as a single piece... but that's just me.
The forestay connects to crossbeam that is also supported by a "dolphin striker" and that needs to be in good shape, otherwise the forestay support can fail.
Rudder shafts on this boat were aluminum originally. I believe the bearings were bronze... this is a galvanic corrosion problem in many cases, and should be checked closely.
I believe the deck is also cored, and needs to be checked for any signs of water intrusion or delamination.
Also, I believe the cabin soles are fiberglass and plywood, so you may want to check the sole for any water intrusion that may have rotted the plywood. I don't believe the plywood was fully encapsulated in fiberglass on these boats.
From what I know of the Edels, they were pretty decent boats with a fair amount of sail area for a catamaran. Windward performance and tacking on them is probably not the best, and you may have to ease the mainsheet to help the boat tack. Weight is going to be your biggest enemy.
I hope this helps a bit.