just bite the bullet and get a decent lens--you want to do it on the cheap, then your pics will show it and you will not be satisfied--sheet film takes expensive time AND money for film these days--you go "on the cheap" and you will just end up wasting money.
the calumet is a good camera--I had one myself--actually, my first monorail camera--very capable and will serve you your whole life--get the same for a lens or you'll just waste time and money.
trust me--you want to be super excited when you see the large format difference...you don't want to look a your first pics and say...hmmm....sharper with my nikon--just spend a little extra money---4x5 lenses--good ones--are not expensive at all. Boards you CAN cheap out on perfectly easily since it's just a square plate with a hole in it...the 4x4's ar easy to make--foamboard works just fine as does craft plywood---just paint the inside black or use black tape
do not cheap out on a lens unless you don't value your time.
AND if you get a decent lens, you'll have no problems selling it for what you paid
you get a junk lens and you can just throw it away as far as tryin to sell it