Budget estimation typically comes from experience or a set of quick calculations.
USM Content
In Resource Management, you can create a new project and assign people (or placeholders for roles and disciplines) for the estimated time required. The resulting future scheduled amount is the estimate for this project.
The project below shows one designer and one developer for two months, at $150/h, totaling $96,000 in billable labor.
Keep estimates and subsequent proposals high-level rather than calculating every minor expense up front.
When the project becomes a reality, this estimate becomes the budget. When you add future assignments to the project, the resulting future-scheduled amount should stay within the budget.
When you schedule too many people or too much time on a project, it will be immediately apparent that this project will go over budget.
If you don't schedule enough people for a project, you may not have the right resources available when you need them.