Paying a lawyer does not cover the government filing fees, which are billed separately and are not returned when a case is denied.

The number on a fee agreement means nothing until you know which forms, which people, and which stage it covers. Two quotes that differ by thousands of dollars often describe different amounts of work.
A fee agreement is the only document in an immigration matter that describes what the client is buying, and it is usually two to five pages long. Most of the disagreements that surface months later were decided in those pages, in sentences that looked unremarkable at signing. The three common pricing structures, a flat fee for a defined filing, an hourly rate billed against work performed, and a retainer held on account, are not competing prices for the same thing. They allocate risk differently. Reading them line by line, with a pen, takes about twenty minutes and settles most of what follows.
The scope paragraph typically names a form, a beneficiary, and a stage. A flat fee for an adjustment of status package might cover the I-130, the I-485, the work permit and travel document applications, and correspondence with the agency through approval. It might instead cover only the petition, with the adjustment quoted separately once the priority date is current. Both are ordinary. The difference in cost is substantial. A careful reader checks whether the derivative family members are named, whether the fee covers one beneficiary or four, and whether the phrase "through adjudication" is defined anywhere in the document.
A flat fee buys predictability, and the office absorbs the risk that the matter takes longer than expected within the stated scope. An hourly rate shifts that risk to the client, which is why hourly billing appears more often in removal defense, appeals, and matters with unresolved criminal or prior immigration history where nobody can forecast the hours honestly. A retainer is neither: it is money held in a trust account and drawn down as work is billed, with the agreement stating how often statements are issued and whether the unearned balance is refundable. The word retainer is also used loosely to mean an initial flat payment, so check which meaning the document intends.
This is where flat fee agreements diverge most, and where a reader should slow down. Some offices treat a response to a request for evidence as included, on the reasoning that a well-prepared filing rarely draws one and the office should bear that risk. Others quote the response separately, often as a second flat fee set when the notice arrives, and a few bill it hourly. None of these is improper if it is written down. The same question applies to a notice of intent to deny, to an interview appearance at a field office, and to a second interview if the first is continued.
Interview coverage deserves its own look. An agreement may include preparation, meaning a session reviewing likely questions and the evidence file, without including attendance at the interview itself, which involves travel and a half day of time. Where attendance is included, check whether it covers one field office or any location, and whether a rescheduled or transferred interview counts as a new appearance. Ask what happens if the case is transferred to another office or reopened after a denial, since post-decision work is routinely outside the original scope and priced fresh.
Filing fees are set and published by U.S. Citizenship and Immigration Services, which is responsible for the fee schedule and for the forms it applies to, and those amounts are paid to the government rather than to the office. A well-drafted agreement says so plainly, states that the fees are the client's responsibility, notes that they change from time to time, and confirms that the office does not mark them up. The same treatment usually applies to biometrics, medical examinations by a designated civil surgeon, certified translations, courier and mailing charges, and consular fees paid abroad. What a careful reader looks for is a line confirming these are passed through at cost, and a statement of who advances them.
Read the termination and refund language, which typically explains how an unearned flat fee is calculated if either side ends the engagement partway. Read the clause on changes in law or policy, since a rule change can convert a straightforward filing into a different matter entirely. Confirm who signs, who the client is when a company pays for an employee's petition, and where communications are sent. Confirm the office's payment schedule, whether it is tied to milestones or to calendar months, and get any promise made in conversation added in writing.
An agreement that survives this reading tends to be one written by someone who has been asked these questions before, and that is a useful signal in itself.