What you get besides getting away
The difference between a residency and working in your home studio is more than just dedicated time and space. Residencies offer an opportunity to expand your own resources, whether in the form of community, support, access to equipment, collaborators, or presentation of your work. Choosing a residency can be similar to selecting a college--it's not just the reputation that matters, but the people, the environment, the alumni support, and the style of the place that makes it a good fit.
Don't get hung up on geography. You can find isolated, bucolic retreats in the middle of a city, or vibrant activity in a rural area. The community within the residency is as important as the external community. But location matters if you're looking for residencies outside your country, if your work incorporates the people and places around you, if you have a limited ability to travel, or if you are looking for a non-residential studio residency in your own community.
For example, choosing a residency program in the heart of Manhattan is sure to offer you a connection to the local community, but what about rural residencies or small towns? How much community is fostered by the residency program itself, and how much is available to artists to pursue on their own? And what if you'd rather work in isolation? Geography alone does not dictate how much connection to community you'll find; instead, consider how many other artists will be in residence (if it's a large group, that may provide its own community), what other programs the organization has in the community (workshops, exhibitions, performances, etc.), and how much access there is to transportation and other means for interacting with others outside the residency.
The total cost of a residency includes whether there are fees required or stipends provided, but also includes the direct costs to you (including meals, materials, and transportation), as well as the indirect costs (loss of income, or whether you're maintaining a home while you are away, among other factors). Many residencies that charge fees also have scholarships available, and most state arts councils have small grants for professional development that can be applied to travel costs and such. For more information, see Fees, Stipends, and Funding for Residencies
Length of time
How much time can you take? How much time do you need? Do you need a long stretch of time to work on a novel, start a new direction in your work, or explore different techniques? Or do you need a short residency to finish editing, jumpstart some ideas, move to the next phase of a project? Do you need a 2-week break while still maintaining your home, job, and family, or a 6-month change of scenery? Residencies can last from a week to a year or more, and the average length is 2 months. Some residencies have a set length, others let you choose how much time you need.
While not all residencies provide living space, many do. The living environments of residencies vary as much as the programs themselves: dorm-style housing, private rooms in a larger house, or individual cabins or apartments; there's also workspace that is separate from the living facility, or living and working in the same space. How meals are handled varies as well, from who provides groceries to who prepares food, how many meals are provided, and whether kitchen facilities are private or shared by all artists. Preparing dinner together as a group can be a wonderful way for artists to get to know each other; for others, not needing to schedule around meals affords them more time to work.
Some residencies provide private studios (like a cabin or an enclosed room), others are semi-private (sectioned-off spaces within a larger workspace), and others have collective workspaces (typically for those media that require specific equipment). Consider your working style, the number of other artists in residence at a time, and at what point in your process you'll be working (some stages may need more privacy than others).
Think, too, about your technical needs. Some residencies provide facilities, equipment and technical assistance that support specific art forms (for example, metal, wood, and printmaking workspaces; dance floors and theater space; recording studios; kilns, darkrooms, and digital media labs) while others offer raw space. Consider what your art form requires, and what stage of your work will be best suited for a residency. For example, if you create artwork that requires large space and equipment to complete, a residency with a smaller unequipped studio may still serve you while you're in the beginning stages of your project.