Re: Crypto mining in general
"From my limited understanding, to be cost effective you have to have masses of specialist equipment designed for crypto mining."
You don't need masses. It's like anything else, you can have one miner or a thousand, just depending on what scale you're going for.
Depending on the base algorithm of the currency you want to mine, there will be a set of equipment that is profitable. For Bitcoin, the algo is SHA-256 and you'll need the latest generation of custom ASICs to be competitive. For Monero the algo is cryptonite which is profitable on multi-core CPUs from the last 2-3 generations (Xeons, i7 and Ryzen) and on GPUs. Etherium uses equihash, and you need a GPU for that.
Your costs are the hardware, power, network and labour. Hence why running your code on someone else's power is pretty good deal (for you), since you only pay for the labour then.
If you're running a rig yourself, then whether it's profitable or not typically come down to how much power costs, and whether the waste heat is useful.
I've got a few rigs that are still profitable, and a couple that are break even but are used as space heaters. For the latter, it's a case of either buying a heater for ~30 euro and paying ~50 cents per day to heat the room, or paying ~600 euro (probably closer to 700 these days) and nothing per day for heating.
"I was just wondering about all the places where electricity comes included in the package."
I would imagine that there is a reasonable use policy for those things. If you exceed that, then you'll get booted off, and possibly prosecuted. A small mining rig is a bit of a contradiction too :) you can squeeze a single card miner into a small form factor, but that will be a bit obvious on the train. Maybe a gaming laptop, but those GPUs are not going to take sustained load without wrecking the fans. While replacing the fans on a normal GPU is maybe 20 minutes work, laptop ones are a bit more of a bugger.
Personally I'm loathe to move a rig once it's running. Once it's set up and running I don't really want to touch it unless it needs a cleaning or I'm decommissioning it. Passive income and all that.
For example a "cheap" 4 card miner with the case closed weighs in at 22Kg and draws 750W, produces roughly 6-10 euro per 24 hours. So assuming you could sneak it into your coffee shop and stay there for 8 hours without arousing suspicion, you could just about afford a cup of coffee. That's a rig that'll set you back maybe 2200-2500 euro or so.