the pocket hammerless colts are excellent guns, made when guns were steel. they have great reputations, thanks to the john browning design.

as for the guns you described to start a collection, pass.... if you want to start a collection, buy guns with a high 90% rating and put them away.

if you wanna shoot them, then buy them and refinish them if you want pretty and then shoot some more.
they are gonna be fine with modern ammo if they have been well maintained.

what to offer?

well the dealer has to keep the lights on and pay the guy behind the counter, he isnt gonna drop the price much, unlike a car that gun will not depreciate sitting there.

start low, see if he haggles, when you reach your best price and he wont budge, shake his hand and leave... if he lets you get to the door, you really were too low.

and for god sake, stop drooling on the gun, he can see it and KNOWS how bad you want them.

last 1908 .380 i saw was 95-98% and was selling for just over $700. actually it was just sitting there under the glass.

+1 what TBFH said. If planning for collection starters be aware there are 4 types of the 1903 model as well as a parkerized 3 1/4" marked U.S. Property serial number range is 554447-572214 are worth nearly double the non military issue pistols.
The model 1908 has 3 types as well as a U.S. Property marked this time in blue finish with serial numbers 134500-138000 they are also worth double or a bit more than the non military.
A word of caution about the military issue on both these models. They are often called generals guns and many were issued to generals, these are worth another roughly $1,000.00 more but must have proof (paper work tying a gun by serial number to a particular general usually) for that premium price.
You best bet is get at lest a copy of the Blue Book of Gun Values the prices may or may not be good but the information should help you not make a high priced new collectors mistake. If you want more information there are a number of good collector guides in print that will tell you what to look for to properly ID Model, type, quantity, and so on.