The rule that governs the general concept of limiting the scope of representation is Model Rule 1.2(c).
The rule language is important. You want to do everything within reason to avoid disputes and problems with the client—and thereby contain as much as possible the risk you expose yourself to in every representation—so make sure you understand this rule and the version adopted in your state. Read the rule, the comments and any other rules that are referenced in either the rule or comments in your jurisdiction.
Paragraph (c) looks simple enough: “A lawyer may limit the scope of the representation if the limitation is reasonable under the circumstances and the client gives informed consent.” There are some important components in that language, however, that, if you do not pay attention, can open you to trouble down the road. Those terms are “reasonable under the circumstances” and “the client gives informed consent.”
In the book, Start and Grow Your Limited Scope Practice: How to Make Money Serving the “Do It Yourself” Client, I wrote an entire chapter on ways to protect yourself both in a general law practice and especially when embarking on a LSR Practice. The good news is that LSR clients are generally more satisfied than traditional full-scope clients and are thus going to be less inclined to complain or file grievances. Get the book, follow the strategies, pocket the results.
You’ll be glad you did!
 Although every action taken on behalf of a client is subject to all applicable rules of professional conduct and other law, this discussion is limited only to the ABA Model Rules and Comments, except where noted.
 Rule 1.2(c).