Attorneys handling home business matters are likely to charge either a fixed price for a fixed amount of work, or an hourly rate. Many attorneys are hesitant to charge a fixed fee for any matter that isn't routine. For example, some attorneys charge a fixed fee to incorporate a company. But, in my experience, most legal fees are charged by the hour for work on business matters. Examples of this kind of work include negotiating contracts with employees, contractors, and suppliers, drafting written terms of sale for your invoices and purchase orders, or sending letters to people with whom you're having a dispute.
Most ethical lawyers do business with their clients in writing.
Lawyers will bill by the hour against the retainer fee in this arrangement. If you're uncomfortable with the terms of the agreement, shop around or get a second opinion. Over time, if you have a good enough relationship with your lawyer, he or she may be more lenient about getting money from you in advance, or about replenishing the retainer fee when it is used. In California, you have a right to terminate an attorney-client relationship at any time. But you're still liable for the bill up to that point.