Border Collies can make fantastic family pets, but as already stated, they require a lot of stimulation and exercise. You will need to be prepared to take them out, not just on lovely sunny days - when the thought of a lovely long dog walk in the countryside can seem idyllic, but also when its cold, wet and windy. When you and your toddler are under the weather, the dog will still need to be exercised.
In relation to insurance, if you go to any insurance website (like PetPlan) and pop in basic details they will give you an idea of monthly cost - its always best to go for a lifetime cover and pay for the highest annual cover you can afford. You should also budget for every vet trip to cost you c£50 (below the threshold for insurance claims), many vets have a 'healthy pet club' where you pay a monthly fee to cover all innoculations, plus a few other things which I can't recall at the moment!
Training classes are (in my opinion) non negotiable for a first time dog owner, they are as much to train the owner as the dog!!
Cost of feed depends upon what you are planning to feed them on - there is cheap supermarket kibble, expensive grain free high protein kibble (like Milles Wolfheart) through to raw feeding which can depend on your supplier, this can be quite reasonable if you have a local butcher.
Be prepared for mess …………… your floors will be muddy, there will be dog hair everywhere, all over floors, furniture, clothes and (yukky) in your food!
I am really not meaning to sound negative, I have a cocker spaniel, who is a gentle, happy but very energetic little dog. He is just 8 months old, and is my first dog, I absolutely adore him to bits but he is a mud magnet, he has eaten all the cushions in my kitchen, dug up the pots on the terrace, eaten all the carrots from the garden and now that he has calmed down, I am awaiting the 'teenage' phase 
I really do love him tho'