Me & my wife breeds alpacas, but we're in Norway so we do not know ur prices for food, dentistry, veterinary visits & so on.
But the alpaca is really easy to keep. It needs about 1kg of hay per day. If u have good pastures, u can replace that with about 1000 square meters per animal. In Maine I am guessing the winter can be a little like here in Norway, so feeding in winter should be hay, alfalfa & lucern pellets (concentrated feed).
Vet care usually is just vaccinations. I will suggest one vet visit a month, but the alpaca/llama r really healthy animals & needs very little vet care. Same goes for dentistry. The teeth can be taken care of by yourself or, like we do here, by the people who shear the animals each year.
If u do not fence them in they will probably wander off looking for food. I would fence them in. They do not need much fencing to keep them in, but the fences r mostly for keeping other animals out. Like dogs & other predators.
They can stay out all year round, but should have a place to go into when they need shelter. This can be just a simple stall. One room & open door. Our alpacas r out all year long, even if the temperature goes below -25C. They r used to temperatures changing from +25C to -30C during a 24h period in the Andes, so they adjust easily.
I feel the llama is a bit too big & strong. The alpaca is easier to handle.