However, there are alternatives. First, after reviewing your case, I would like to agree with you on what the final cost of services will be, in other words, a flat fee. Or, agree with you in advance what it would cost for completion of each major step in the case. Seems to me that would give you a yardstick to measure whether the next step is worth it. What do you spend, what can be gained?
Second, if you want services that are limited to a few tasks, then let's agree on what you need and what I can provide. Sometimes all you want, or need, is some advice, review, or preparation.
If it is important to you that the services provided fit within your budget, I want to work with you.
In most circumstances, you will be asked to provide a retainer. The retainer is used to begin work on the case, and to pay any necessary court filing fees and other costs.
Irrespective of the arrangement, you will be required to sign a written contract that sets forth the extent of the services and the fee charged.