I looked into it a bit more and can see where there can be confusion on this.
This article is quite informative:
http://www.meeb.com/legal_alert/legal_alert_09_04.htm
Essentially it says that there are HUD requirements that specify that for a community to be a 55+ community (and thus be allowed to discriminate against children), the developer/association MUST restrict occupancy to those under 55 to no more than 20%. HUD does not specify a lower limit as to the age of these 20-percent buyers. However, it DOES give leeway to the developer/association to be MORE restrictive on this if they desire. In other words, a developer is allowed to mandate that ALL residents must be over 55 if it desires.
Where I got the 50-year lower limit was from another developer who obviously imposed this as his lower limit on age (i.e, at least one person must be over 50 and that no more than 20% of the houses could be occupied by households whose oldest member was between 50 and 55). What I have not seen in writing is what TV's rules actually are. They may also have a similar restriction on at least one member of the household must be over 50 ... or they may allow any age as long as they maintain the number of households under 55 to no more than 20 percent. My gut (and my fading memory from discussions with our sales agent) tells me that TV also imposes a 50-year lower limit on the oldest member of the household. However, it certainly is worth looking into if you don't meet the 55 age limit. Apparently every developer can have his own rules as long as he maintains at least 80% of the units with at least one person above 55.