Keeping things in order is one reason to have a desk in your home. What do you do with your bills every month? Have you got a system in place? A desk could give you a place to keep them filed every month. One place for items to be paid and another file for 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.
Desktop computers are in most homes these days a place to put those monitors is usually a desk. The monitor could sit on other pieces of furniture, but the height might be wrong or there might be other issues that would not come up if a desk were being used. Some of those are adjustable for comfort. You may not get the extra space for writing and such with this type unit.
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.
Spacing in your home may be what makes the decision for you. If you have an entire room to work with, one of the larger units such as the L shape or the corner unit would be great. However if all you have is a corner to use, then one of the adjustable units would hold your monitor so you could work online in comfort.
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.
Purchasing a desk for your home is an investment so take your time and compare the offers. Look for the best deal all the way around. Consider how long something may last and what you want to use it for. Look at all the angles before you purchase so you can make an informed decision. Then enjoy your purchase.