When a business takes on a large job - one that involves buying materials, committing time, or turning away other work to do it - the way the payment is structured decides who carries the risk in the meantime. The default many small businesses fall into is to do the whole job first and invoice at the end, which means funding everything themselves along the way: paying for materials, covering labour, and waiting, sometimes for weeks, to be paid after completion. If the customer pays late, disputes the bill, or does not pay at all, the business has already spent the money and is left chasing it. All of the exposure, for the whole duration, sits with the party that can least afford it.
Asking for a deposit or a staged upfront payment shifts that balance to something fairer. Taking a portion of the fee before starting - and, on longer jobs, further payments at agreed milestones rather than everything at the end - means the business is not financing the customer's project out of its own reserves. The upfront money covers the materials and initial costs so they are not coming purely out of the business's pocket, and the staged payments keep cash coming in as the work proceeds rather than in one lump at a distant finish line. For a small business, where cash flow is often tighter than profit, this timing can matter as much as the total amount.
Beyond the money, a deposit quietly does something useful: it confirms the customer is serious. A client genuinely committed to a job has little problem with a reasonable deposit, because they intend to go ahead and understand that the business is about to commit real resources on their behalf. A client who balks at any upfront payment at all is, sometimes, one who is not fully committed, is shopping around, or may be a problem to be paid later - and it is far better to learn that before laying out money and time than after. The deposit acts as a small filter that separates the serious from the tentative at the point where it costs least to find out.
Handling it well is mostly a matter of being clear and normal about it. A deposit should be a stated part of the quote, not an awkward afterthought - a plainly explained term, in writing, of how and when payment is structured, so the customer agrees to it up front as a routine condition of the work. Most customers accept staged and deposit-based payment readily when it is presented as standard practice, because it is. The businesses that get caught out funding large jobs and chasing payment afterwards are often the ones that never asked for anything until the end - and the simple discipline of taking a fair deposit before committing resources removes a great deal of that risk before it can arise.