Years ago I was in your position with my first startup. For free, a lawyer (Lawyer X) helped me start and document my ideas and business; became lead counsel under engagement with his large law firm; asked for and was granted management shares (Class B, C and D); was voted Secretary of the Board; became a non-voting Board Manager; managed up to 15 lawyers who handled all of our legal work; named as the Executor of my Will; and became a good friend.
When my new company was valued over $400 million Lawyer X then left his law firm and joined the institutional investor who had funded my company - as a partner and managing director. He switched from being our corporate, and I believed personal lawyer, to being my boss. He later became president of the institutional investor. He then got ownership in the institutional investor's shares (Class A). Within a few months after being our lawyer he owned all classes of shares (A, B, C and D) (big conflict), and became a voting Board Manager; member of the investment committee; and failed to remedy a long standing default by the institutional investor regarding managements' class C and D shares - in an operating agreement that s/he drafted.
Bottom line her/his status went from serving a "prospective client" (State Rules of Professional Conduct) to "defendant and counter-claim plaintiff" in a series of very large law suits in Federal District, Federal Appeals and State courts that spanned seven years. As a Wharton MBA and Temple Law graduate I should have known better. So-called "service bartering" is generally a very appealing approach but can be a very bad idea. At a minimum you should understand your risks and the rights of a minority shareholder.
Never again have I used so-called "free counsel" for my start-ups. I have obtained seed money (can be good idea) or did the documents myself (also a bad idea but better than the other bad ideas). Nothing is free and, if the money gets big (value of your and Lawyer X's shares) the complexities of the relationship are massive, and the winner of any disputes will likely be the party with the most money for legal fees and costs. It is unlikely it will be you.
Further, it is unlikely that a good lawyer (one who has a written legal duty and skills to protect you) will conduct free legal work without an engagement letter for equity. Also, keep in mind that once you sign an engagement letter with a lawyer's firm your "free friend" no longer represents "you" - 99% of the time s/he will represent the company.
I could write a book on issues that can occur if large money becomes involved and your lawyer's loyalty is to money in his/her pocket and not the original founder. In my view, the duty will always be to your company and money in her/his pocket - not you. There are lots of rules of professional ethics on these matters, none of which really matter in a serious dispute.
If you want to contact me I will discuss "business advice" on how to handle your issue. However, I cannot and will not give legal advice.