This is just my opinion, but personally I turn and run when I come across a landlocked parcel with no legal easement. The only way I would pick one of these up to try and resell would be if I was literally getting it for, like you said, next-to-nothing and even at that I would do an option agreement as opposed to buying it outright.
Buying on an option, like a lot of things with raw land, is different than it is with SFRs. Typically, on a house you're gonna end up signing a contract that says you'll close within 30 days of execution -- I'm sure that number varies, but that's what I've dealt with. What that means is that you have to do all your due dilligence plus line up a buyer all within that time frame. You could ask the seller for more time, but in my (limited) experience if a seller is willing to sell you their house for enough of a discount that you can flip it to a wholesaler and still make a profit, that seller mostly likely wants to close asap.
Now, on a land deal, the seller is much much more likely to give you a larger window of time to line up a buyer so you can do your assignment or simultaneous closing. The option agreement I present to a seller whose property I can't or don't want to pay my own cash states very clearly and in an upfront manner that for the next 6 months (sometimes longer) I will market their property and find a buyer who will be willing to pay the price they're after. I have both exclusive (meaning they cannot sell the land to anyone else during the duration of our agreement) and I also have a non-exclusive, just in case they're not comfortable tying themselves down to me. The truth of the matter though is that most of the people I buy from have owned the land since forever and have done nothing with it, so what's another 6 months?
The TL;DR version is this: if you use the proper paperwork (purchase w/ an option) you definitely do not need to close on the land before you market it and line up a buyer. You're right about the neighbors being your best bet, though depending on the location of the parcel, I have heard of some people putting billboards up on their crap pieces of vacant land and renting the billboard space out...
Hope that helps a little