I would add that while 35mm is almost always developed in daylight tanks, 4x5 film is often developed in complete dark (as with the hard rubber tanks mentioned. There are daylight tanks for 4x5, but less common than for 35mm. Research here and on the LF forum will help clarify the advantages and disadvantages. Keep in mind that you need a lot of chemistry for some tanks, which can be difficult to justify for a few sheets at a time unless you are developing frequently. I suggest investigating the "taco method", tray method, and homemade developing tubes as options.
I would second the idea of using 120 film in a roll film holder, but keep in mind that you will make your lens seem a lot longer (i.e. a 90mm LF lens goes from roughly 28mm in 35mm equivalent to 50mm).
Don't neglect a decent tripod. Much has been discussed on Apug about tripods.
Do some research on lens coverage - not something usually considered in 35mm. Difference lenses will have varying angles of coverage. And your need for coverage will depend on your usage (i.e. if you use a lot of movements).