There are some minor restrictions in the D3 manual about contact at the student athlete’s school (see below), but I agree with adbono that this is mostly a matter of protocol with his juco coach. Each coach has his own way he likes to do things, and if the player wants the coach's help, he should try to play by the coach’s rules. I would suggest that he talks to the coach soon and gets his blessing (and advice) about contacting D3 coaches. That should just be a formality, then he can start making direct contact or the juco coach may want to initiate the contact. As far as timeline… he can start now, with the goal of getting schools to evaluate him during the fall season. D3s will be trying to lock up high school kids in the fall, so he needs to be on their radar before they fill those spots.
13.1.4 Contact Restrictions at Specified Sites.
188.8.131.52 Prospective Student-Athlete’s Educational Institution. Any staff member and any representative of the institution’s athletics interests desiring to contact a prospective student-athlete at the prospective student-athlete’s high school, college preparatory school or two-year college first shall obtain permission for such contact from that institution’s executive officer (or designee). Contact may be made only when such permission is granted. Permission for such contact is not required if the contact with the prospective student-athlete is made after official school hours. Member institutions also are bound by this provision when recruiting international athletes. [D] (Revised: 7/21/09)
184.108.40.206 Practice or Competition Site. Recruiting contact may not be made with a prospective student athlete before any athletics competition in which the prospective student-athlete is a participant on that day of competition until the prospective student-athlete is released for that day by the appropriate institutional authority(e.g., prospective student-athlete’s coach or comparable authority). Further, telephone calls or electronic communications may not be made with a prospective student-athlete at the site of organized competition involving the prospective student-athlete by athletics personnel who are attending the competition or who are aware of the competition. [D] (Revised: 1/11/89, 1/10/91, 1/11/94, 1/9/96 effective 7/1/96, 12/19/13, 1/17/15, 1/21/15, 1/16/16)
220.127.116.11.1 Exception—Official/Unofficial Visit—Contact on Institution’s Campus on Day of Competition Prior to Competition. Athletics staff members are permitted to have on campus contact prior to competition with a prospective student-athlete, provided the prospective student-athlete is not scheduled to compete on that day on the institution’s campus. (Adopted: 1/16/16)
18.104.22.168.2 Contact with Prospective Student-Athlete’s Relatives or Guardians at Practice or Competition Site. Recruiting contact may be made with the relatives, guardian(s) or individual of a comparable relationship of a contactable prospective student-athlete (see Bylaw 13.1.1) at the site of the prospective student-athlete’s practice or competition, including during the conduct of a competition. (Adopted: 7/21/09)
13.1.5 Evaluations. There are no restrictions on the number or timing of evaluations (see Bylaw 13.02.4). (Adopted: 4/20/09)