From the TTB:
Title 27
§ 25.205 Production.
(a) Any adult may produce beer, without payment of tax, for personal or family use and not for sale. An adult is any individual who is 18 years of age or older. If the locality in which the household is located requires a greater minimum age for the sale of beer to individuals, the adult shall be that age before commencing the production of beer. This exemption does not authorize the production of beer for use contrary to State or local law.
(b) The production of beer per household, without payment of tax, for personal or family use may not exceed:
(1) 200 gallons per calendar year if there are two or more adults residing in the household, or
(2) 100 gallons per calendar year if there is only one adult residing in the household.
(c) Partnerships except as provided in § 25.207, corporations or associations may not produce beer, without payment of tax, for personal or family use.
(Sec. 201, Pub. L. 85-859, 72 Stat. 1334, as amended (26 U.S.C. 5053))
I have never seen a restriction on the sale of brewing supplies/equipment, at least not in Calif.. Interestingly, there is no requirement for a brewery/distiller to ask your age for access to their website, though most do for some reason.