Realistically how much money are you gonna make from boarding guinea pigs? 50 quid a month?
Yo can make a living from only couple of acres of farming - I have seen it. But you have to grow quite intensively and quite high value crops. For example to make a living from growing just baby greens and salads all you need is a largish poly tunnel or two. At the same time plant some fruit trees in between vegetable rows and have some (100-1000) laying hens as this is very easy to set up and manage.
At the end it's all about the marketing. You can sell those 1000 eggs a day to supermarket for pennies or convince people that these are THE BEST eggs they can ever taste - pastures hens that graze fresh herbs and grass every day and have never seen a massive ugly industrial barn.
That s what we are planning - egg laying hens in a movable coop (old trailer chassis) following couple of cows and sheep which are also moved every day to a new paddock.
Meat chickens in small movable coops again moves every day to fresh grass.
We have an advantage of living right next to the city of Leicester 30miles from Nottingham, Coventry, Northampton, Peterborough and 40miles to Birmingham to within 1 hours drives we have at least 3 million people! You can't say that in some other parts of the country though.
I know people who make a living farming 1.5 acres of just vegetables - however - if you wanna grow that much potatoes or other root veg - forget it. You would have to grow a lot of salads and greens - they grow fast so you have a quick rotation and they are relatively expensive per kg.
You could have veg box school, sell to restaurants (contract), farmers markets etc