Susan, ferals and strays are literally everywhere. Shopping centres, fast food places, farms, garden centres, apartment buildings, back gardens, schools, universities - almost always outside. They are very good at keeping away and often only come out at night because of all the hustle and bustle that goes on during the day. You have most likely visited these places without even knowing ferals live there. Sometimes they are left to exist on their own, scrounging for food and breeding freely and sometimes there are managed colonies where the cats are fed, given medical treatment, vaccinations and TNR'd (Trapped, Neutered/Spayed and Returned).
Most strays and ferals look thin if they're not in a managed colony but really, apart from that, look pretty normal unless they are sick or injured. MA's (hissy's) ferals are all part of a managed colony. If they are very feral and not able to be rehabilitated or rehomed, they become part of MA's colony, where they are wonderfully cared for. These cats never come inside the house and are only trapped (often with difficulty) when they need medical treatment. There is another level of ferals where the cats are still part of the colony but are OK to be petted and touched by MA (usually after a long and involved process of the cat learning to get to know and trust MA), but still live outside. Cleo is one of these. MA also has cats that are former ferals. They are inside/outside 'house' cats. Sometimes they have behavioural problems which other people are not willing to deal with, so they become part of MA's family.
MA, please correct me here if I haven't explained something properly.