Here is what you have. Look at the attached picture, 2nd row down, and from left to right you have an 807 caboose, 803 hopper car, 804 tank car, 805 box car and a 252 locomotive. As "Papa" Eastman indicated this is a set from the late 20's or early 30's. In the condition shown in my attached picture with the 252 a very good runner and having wheels in very good condition, the set would be worth any where from $240 to $300. Keep in mind the market is very soft right now and it would be hard to come up with a precise value.
In the condition your friend's appear to be in, as is, and if the locomotive ran and the wheels were intact and had not started to crumble, you might value it at $85 to $100. If the locomotive did not run or needs new wheels, much less. Hope this helps.
Jim
Sorry, I forgot to add the attachment on my initial post so here it is!