The Office of the Massachusetts Secretary of State will permit a person(s) to establish a Massachusetts Limited Liability by simply submitting an on-line form: https://corp.sec.state.ma.us/corp/FilingForms/0801024.asp?stage=DataInput.
Submitting this form, without otherwise formalizing the relationships among the persons participating in the limited liability company, subjects those persons to the provisions of Massachusetts General Laws, chapter 156C. This chapter is extensive and persons forming a limited liability company who are unaware if its provisions are operating in the dark and at risk of being disappointed--perhaps significantly so--by application of its provisions. You can find more information here.
Don't allow the ease of forming a limited liability company to lull you into concluding that the matter is a simple one.