Fjos is correct - if you are not connected to the mains you don't pay for water. But you do have to pay (for materials - and tools and labour, if you can't DIY) if exterior/underground pipes freeze and burst or simply spring a leak, and it's sensible to save up to replace water storage tanks/pumps/pipes every so often. In some regions of Scotland, if more than one house is connected to the same private water supply, then the local authority reserves the right to test the water to make sure that it's safe to drink. This can cost almost £100 per year. A good septic tank may never need emptying, but if it does, a single visit from the tanker can cost £200-£300 or more, depending on location and how urgent the problem is. Mains water is cheaper, on the whole.
Solar panels are great, but they are a long-term investment and can be quite costly to begin with. (I know OP has mains electricity, so this doesn't apply.) Bottled gas is handy in a power-cut but very expensive.
Other things to think of include fencing (not cheap) - to keep out sheep and deer - and strong gates (ditto), maintenance for any private road/pathways, wind-netting/rabbit guards to protect newly-planted bushes and trees, plus the cost of getting woodfuel delivered (and of building a shed or lean-to to store it in the dry; it burns much better and pollutes less if it is well-seasoned). Delivery costs for other things - eg for bulk porridge oats, pulses, nuts - can be very high, and couriers don't call every day.
If you like fresh greenstuff and salads, it can be a problem to ensure a year-round supply unless you have a polytunnel/greenhouse. Plus, ideally, 'daylight' electric lighting, since many leafy plants don't grow well in dark northern winters. On the other hand, absolutely nothing stops kale ... And, even if you fancy a once-a-fortnight trip along icy, single-track hilly roads to the nearest supermarket - ours is almost 60 mile away - that's not always the answer. 'Just in time' supply chains means that many shop-bought salads/fruits/veg etc have a very short shelf-life. They won't last long once you've got them home
As other rural dwellers will know, there is still no mobile phone signal and no broadband in many places. Satellite broadband typically costs around £50 per month fro a small household; it is relatively slow, can be disrupted by bad weather and downloads are almost always strictly limited. Petrol costs much, much more than in towns.
As others have said, it's great living a remote place, but it's not cheap and it's not always easy.