Hi
A single goat and a kid should be okay - ideally would keep 2 adults but at least neither is on their own.
Hard feed - there is so much choice - goat coarse mix is too expensive for me as I have 30 but if only 2 then maybe a good start. It will be balanced. Not sure how much you should feed - depends on condition of goat and kid and if she is milking.
Need good quality forage all time - hay, can use barley straw - but hay best - especially for a milker I would say
My goats not destructive to buildings too badly but some have chewed wood. They will eat bark off trees so these will need to be protected depending on the species
Milking - well you are on same journey as me. I have a metal bucket, a sieve for sieving the milk and you will need somewhere clean to do it away from the bedding and ideally a raised area ie stand for her - better on the back
Books - loads around - Alan Mowlem one OK. Best one for vet things is Matthews book but is expensive but well worth it