Your lifestyle could determine if you must have a desk in your home or not. Are you organized? Is there a place for everything and everything in its place? Where do your monthly bills get put? A desk would be a great place to file them every month so come tax time you would have everything in one place. You could have a file for items to be paid and a file for those that are paid.
What you can or cannot do, will be determined by the style of the desk you decide on. If you purchase a computer unit it may only hold a monitor and have no room to do anything else on it. If that is the case paying bills may need to be delegated to the kitchen table every month and the bills stored in a box in the closet.
Most homes these days have a desktop computer and a desk to place the monitor on is almost an essential. You can use other places to put the monitor but it may not be as comfortable as having the proper set up that a computer unit would give you. Some of the computer desks are adjustable for heights to make them more comfortable to sit at. However they may not offer the extra space for writing and doing other office duties.
You might want to get two of these if you have the room. It would be ideal if you can have one for the computer and one for every day work. The one for the computer could be one of the small ones that only the monitor would fit on to save on space if it might be a little snug.
A larger unit could encompass both of your issues. An L shaped or a corner unit would be large enough to place the monitor on top as well as have room to do desk work. There are also units that have matching credenzas to give you extra space if that is the style you are looking for and you have the room.
The space in your home that you have available for this may determine which direction you go. If you have an extra room to fill then you could consider the executive style, two units or the credenza. However if you are going to set the work station in a corner of an already busy room then you may want to get the unit that only holds the monitor.
Another factor on your decision may be the cost. If a budget is in the mix shop around. Online stores tend to offer better prices than offline but you have to consider shipping costs. If a local store has an online presence also, sometimes you can get their online sales, and then ask to be able to pick it up to save shipping costs.
Compare prices from the different stores online and offline. Watch for the deal that gives you what you want. Research it out and then make an informed decision. You can then rest assured that you made a good choice.