I am wiring up a small office building on side of my house. I am running 240v to a sub panel in the office. The office will have 4 outlets with computers, printers, and the like plugged in; an outlet with a 5000btu Window unit ac; and a light, ceiling fan, and outdoor fluorescent light. The breaker box I have for this only has the "hot" bus and a neutral bus bars. I have read conflicting instructions as to if I can have the ground and neutral terminate on the same bus bar.
1. Can I have both neutral and ground wires on the same bus?
2. Is it dangerous to have them on the same bus or only ugly work and not neat?

Is the office a remote structure or part of the original structure?

If the office will be in a remote structure, you must us a 4 wire feed to the structure.

Also, the building must have its own grounding system.

At the downstream panelboard, Neutral and Ground must be isolated. Basically that means you cannot connect neutral conductors to the ground bus or ground conductors.

If you do not know how to do this to code, please consider contacting a licensed electrician. If not done properly, you risk fire and or serious injury.

According to current code, a subpanel must be set up with a ground and neutral bar. You would need to use a 3 conductor wire with ground and install ground rods at the office, if it is detached.

You can purchase a grounding buss and install in your sub-panel.

According to code - you must use a 4 wire conductor from the main service panel to a secondary panelboard.

If the downstream panelboard is in the same building it can be tied to the existing grounding system. However, if the downstream panelboard is in a remote structure, you must set up a separate grounding system in the remote structure.

homeowners should be aware that the law allows us to do electrical work on our own
personal dwellings but it also requires building permits which include electrical. A small office may not be considered part of the dwelling so professionals may be required.