You can often find Griswold and Wagner Cast Iron on Ebay, or at garage sales, cheep. My favorite Griswold was given to me by an antique shop because the owner was impressed that I new the pan's quality. He'd had it on display in his shop for better than a year and couldn't get $20 for it. The other Griswold pans came to me cheaply. I paid $30 to my boss who was renting his home to an acquaintance of mine. I was helping the family move into the home and noticed three nice Griswold pans in perfect condition sitting in the entryway of the house. I asked him if he would sell them. I even told him that they were collector's items and offered to look up the value on the internet. He sold them to me for $30 on the spot. That's where I got the 5 1/2 inch pan, and another ten inch, and a twelve inch pan. I kept the smallest of the three, and sold the other two pans to my professional chef son for $20 buck. He was thrilled to get them.
As far as seasoning, if you're lucky, you just have to rub with oil or shortening, inside and out, and place in a 350' oven for a half hour or so. I prefer to fire up the grill and place the pans over the hot charcoal and let them cook for a half hour, re-rub them with oil and repeat. It really bakes in the fat to a smooth, slick, and hard surface. It also keeps me from smoking up the house.
IF the pan is in rough shape, and rusty, simply hit it with a wire brush, or fine sandpaper. I've cleaned up badly rusted pans with a wire wheel attached to my drill. Then season as described above. You may have to put three or four layers of seasoning on the bare metal to get that really good seasoning that is so prized. But once it's there, it's so easy to maintain. And it gets better every time you use the pan.
A common rule of thumb is to not cook acidic ingredients in cast iron as the food will take on a metallic flavor. My pans are now seasoned well enough that I cook acidic foods, like marinara sauce, pineapple sweet and sour sauce, and other dishes like that, with abandon, never having to worry about the food acids reacting with the metal. The actual metal is hermetically sealed by the polymerized fat and keeps the acids, or alkalies from ever touching the metal.
I've even been known to take my pans camping, and scour them with sand and running cold water. We did that all the time with such pans when I was in boy scouts so many, long, years ago.
Lodge pans are great pans too, but take longer to get that really great finish due to the rougher casting of the metal. The inside texture is more grainy than is the inside surfaces of either the Griswold or wagner pans. It still works the same way though.
Seeeeeeeya; Chief Longwind of the North