The scientific name is Morus alba (white mulberry - alba means white) there is also Morus rubra (red mulberry - you guessed it, rubra means red 
For $6.95 they are probably quite small. They are fast growers (11'-12' in 4-6 years) but you'll still have a bit of a wait to have a constant supply of foliage. Did you say if you are in northern or southern clime? Silkies eat A LOT!
As for fruit - it doesn't matter which you get. Most mulberries are dioecious, which means the male and female flowers are on two separate trees meaning you need both to produce fruit. However some are monoecious - both male and female flowers on one tree. Since you have many in your neighborhood I am sure cross fertilization will take place and if you have female trees they will produce fruit. Two notes about the fruit - they are absolutely delicious! Second, they are very messy (drop a lot and smoosh!), but the birds love them too. So if any of these are a concern try to get a male tree (provided the nursery has them sexed) since it is the foliage you are interested in.
Sorry about the science lesson but if you are considering growing them you may as well know the basics. Another thought…you said they were growing on your property? You could find a sapling that is farther along than nursery stock and transplant it closer to your house. If you choose to go out and collect them they do stay fresh in the fridge for several days.
Hope I haven’t confused you!
lele
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0.1 veiled - Luna
0.2 green anoles Jaida & Jetta
0.1 brown anole - Jamaica the j sisters were sent to freedom last month
0.2 house geckos - Gaia & Tia (MIA 
0.2 felines - Kyndra and Líta