"...an ancestor who was a tenant farmer in the 1880s"
Things were very different indeed 150 years ago, and even more recently as well.
Unmarried women and girls being in service was very common indeed. Also, agriculture was a lot more labour intensive than it is nowadays.
For example, one ancestor of mine worked as a domestic servant for a farmer and his family who was described as a "Farmer of 40 Acres employing 1 man and 1 boy".
Nowadays, 40 acres wouldn't generally support one family never mind also two employees and a servant.
Farmers with larger farms would employ proportionately more labour and also more servants.
"I have an ancestor who was a clerk. Lived in a 12 room house with two servants."
Again, this was not unusual, but I would suggest that he was likely a bit more than just a clerk. Most middle class families employed domestic servants. An ancestor who worked for HM Inland Revenue employed a domestic servant in the 1890s and 1900s. At the time of the 1901 census they were living at 111 Hopton Road, Streatham, London which you can see on eg Google Maps to see the actual home they were living in.
One of their sons became a doctor, living on Ealing Road, Wembley and this son and his wife also employed a domestic servant right up until the 1930s.