You might want to get a proper safelight - they're low wattage (usually those little 15W bulbs) and are known safe for photographic paper. A.N.Other red light bulb (if that's what you were meaning) might not be suitable - possibly too strong, and the spectrum might extend too far beyond red to be safe.
5x4 paper is quite hard to find (I could only find that size in direct positive when I was looking recently), but you could use 7x5 and trim, or get some 10x8 and cut it down to 5x4 (or contact print four negs on a 10x8). You'll also need some trays to match the paper size - at least 3 (dev, stop, fix) and somewhere to wash the prints after fixing (sink with the tap running at a rate no higher than the overflow - give them a regular wiggle to keep them separated). RC paper is easier to wash than fibre, and readily stays flat. Somewhere to dry them as well - maybe a tray or bit of board with a thin towel spread over it to make a flat, absorbent surface. Put the prints on it face up.