Living completely off the grid is possible but requires a lot of work to provide the stuff the big utilities sell you.
Mobility will have many drawbacks as well unless you have good work at all times or a healthy bank account.
Depends on what you're prepared to give up - I miss baths, but I have a shower.. I can live with an inconsistent TV signal while the tide's in and it's windy.. I now have to find my land-legs way more often than my sea-legs.. takes an hour to fire up the wood stove as I don't have central heating..
You definitely do need to be handy though - carpentry, plumbing, electrics, mechanics.. unless you have loads of money and can pay someone to do stuff - but why would you need to live off the grid then?
I'm in the process of renovating an old boat I bought to live on. I got it seaworthy, now I'm refitting the interior - including electrics, plumbing, mechanical and electronic instrumentation.
I've lived aboard for over five years now and have avoided some costly debt and homelessness since I became ill and unable to work - I was able to move from a marina to a cheaper mooring while I waited four months for my benefits to come through so I didn't fall behind on fees, rent/bills cost me about £120 per month, compared to £600-800 when I had a house, so my savings stretched far enough to allow me to eat.
In the UK liveaboards don't pay tax for services - because we don't get any services.
I'm currently plugged into mains electric provided on the mooring I occupy, but I'm working on a wind turbine, solar panel, battery bank and inverter so I can disconnect if I need to. I also have a diesel generator and calor gas onboard. My electric bill is only £10 per month, compared to about £50 my folks use, as we just pay for electric used - no service charge - and more economical useage in the smaller space.
I also have plans to collect and purify rain and river water in a solar still for washing and drinking.
I'm building up a store of dried and tinned food in case of shortages - my own or the countries'. For the first year I was claiming initial base-rate benefits I could only afford to eat 3-4 small meals of plain pasta a week - I'm determined I won't get caught being dependent on the state like that again!
I plan, eventually, to move the boat to a wide stretch of river and drop anchor, as I won't then have to pay mooring fees, as the river below the low tide mark isn't owned by anyone.. free living.
I think this is a good idea, but you should also check out the laws in your area, because some local governments do not like people going off-grid. Regardless of why, it's important to check.
There was a case in the UK recently of an elderly woman who owned her own house and land in a remote location and was completely self sufficient - she had a well, generated electricity, grew vegetables - and sold some to give her money if she needed anything..
Her local council took her to court and she was made to pay a yearly fee - I think it was around £500 - as she wasn't contributing to the economy!
It's much harder on land, these days, to get away with this sort of thing, but on the water - you're untouchable. I and plenty of others have been threatened with legal action by local councils for living illegally, but we're not - we're just living outside the reach of national law and within the perview of maritime law, which is completely different. Also, those councils would be obliged to house 20,000-30,000 people even if they did manage to contravene maritime law.