Deposit
A deposit is the part of the price a client pays upfront, before the work starts, to secure the project and cover the provider's early costs.
It usually covers what the provider spends before delivering anything: materials, subcontractors, early hours of work. Its size is set in the contract or the quote, as a percentage or a fixed amount.
Rules vary by state and by trade; check yours. California, for example, caps the down payment on home improvement work at $1,000 or 10% of the contract price, whichever is less (CSLB).
In a Seequence, a short first step, validated then paid, can play the role of the deposit, with a concrete content instead of a percentage.
Example. On a $30,000 quote, a 50% deposit means $15,000 paid at signing, before any visible result.