My first question is what is the average price for a Morgan or Peace dollar. I am trying to find common date g4 to vg8 of those two. Also I am wondering how easy is it to find walking liberty and franklin halve dollars in rolls? Lastly, what is the price for common dates of those? Thanks.
In the grades and types you mention, those are basically bullion "junk silver" coins. Major bullion dealers like gainesvillecoins.com post prices for singles, rolls, and bags every day. Today, June 29, you can buy the half dollars you mentioned for roughly 20.8 times face value, don't know about freight costs. Low-grade silver dollars also trade as bullion, today quoted at $25 to $28 per coin (each 0.773 Troy Ounce). Which begs the question, why pay that premium? You are extremely unlikely to find silver halves in rolls, although it occasionally happens, due to theft of a coin collection, or sheer ignorance on the part of a reclusive hoarder.
Until silver's run-up a few years ago, it was actually fairly common to find silver halves in rolls. Since they barely circulate, and since most vending machines and self-check-out counters don't accept them, people tend to accumulate halves for a long time and then dump them at the bank. Over the last few years, "the secret has gotten out", and at this point halves are nearly as heavily picked over as other denominations. But people still come across old jars of change and turn them in at face value. (A quote I've heard from more than one teller: "I told them they could get more money at a coin shop, but they said they didn't want to go to the trouble/don't trust coin dealers." I'll go to a lot of trouble to get $180 for a roll instead of $10, and I do trust coin dealers to pay me considerably more than face for silver.) Finding good stuff is just a matter of being at the right place at the right time, or befriending tellers who don't want to grab good coins themselves. There's a separate "coin roll hunting" forum here, with a gargantuan thread where people post their circulation finds. For some reason, posts to that forum don't show up in the "Recent Posts" list; you have to go and look for it.
You mention that you are looking for grade 4 to 8. If you are looking to collect, not just looking for silver, you can get better grade coins for the same "melt" value. You can often get grade 40 for the same price as 4 - 8 just because of melt values.