Mark~ You can get zoanthids/palythoas with one polyp or one hundred polyps on them... And I've seen some with more than 8 different morphs and a thousand polyps on one rock... Personally I prefer to purchase rocks with only one color/morph on them... The problem that sometimes occurs with multicolored rocks is that one dominant zoanthid will spread faster and usually overtake and choke out the other... That is not always the case however and multicolored rocks can be the most beautiful...
As camaroracer stated, growth rates can vary quite a bit... I received a frag of 3 PPE's and 3 Nuclear Greens at the same time... By the end of about 6 months I had 12 PPE's, and probably 30 Nuclear Greens... I have some zoanthids that will grow even faster than that...
Off topic: Where in East Tennessee are you??? If you're somewhat close to the Knoxville area, you should think about joining the ETRC... If you're closer to Chattanooga, consider the CRC... The ETRC has a forum on here... CRC keeps theirs on another site... PM me if you're interested in joining a local club... I think there is one up towards the Tri-Cities too...