I faced something similar, but with Velvet, far nastier than ich. Steps I would recommend.
Freshwater dip all fish ASAP. Rodi water, match temperature, put fish in for no longer than 5 minutes. This kills the parasites on the fish giving you extra time to work and gather supplies.
Go and buy a sturdy plastic tote/bin, fill with water, matching salinity and temperature. Depending on the size of the bin you can do the following.
A: Transfer your fish into the bin, add a sponge filter, powerhead, heater, seed with bacteria from your filtration set up. Not you can dose copper or whatever medication you want for as long as you need to.
B: Transfer all your rock, sand, corals, inverts to the bin, set up lights, powerheads and heater, and you can now dose your tank with the fish with whatever medications you want.
C: Go the Ich Management route, there are several good threads about it here.
This won't take up much space, and can be set up quickly and for less than $50. It's what I did to save my eel as they're very copper sensitive, but parasite resistant. He is quite happy living in a big bin with nothing but live rock, a light, powerhead and lots of water changes. Total floor space used is less than 2 square meters, can legit be set up in a closet.
Just be sure to keep your rock/coral/inverts fallow for a minimum of 76 days, longer if you can manage it.
Prolonged exposure to saltwater can weaken some plastics over time. Keep an eye out for cracks and leaks. This happened to me, but fortunately I caught it pretty quick.
Attached is the picture of my setup. Well, it's a picture of my cat pretending to be a porpoise, but you can see it in the background. Doesn't take up much space at all and I have 50lbs of rock, snails, hermits and an eel in there.
