I wish forums had been around when I started in 1977 but they weren't so I had to learn as I went along. For a start I was in a Halcyon 27 with a partner (for a few years) which is almost a dinghy compared to the usual size of yacht now-a-days. The partner was replaced numerous times over the years but that's another story.
One thing we didn't have was electrcity so I used a 2 kg propane bottle with a mantle lamp which provided more then enough heat and lots of good light for reading. Had to leave the central hatch open for ventilation and keep the heat down. This caused condensation but a few hours with the companionway open every day or so solved that.
For showering we used a l0 ltr "Sunshower" bag half filled with water from the tap and a kettle fulll of boiling water suspended from a cleat on the mast outside with the shower head led down through a dorade vent.
We/I lived for 17 years in the eastern Med with about £300 a month working when ever work was on offer which wasn't all that often but if so any funds was used for "extras" or banked. I divided by monthly income by 5 and drew 20% every Monday - half went for house keeping and the rest for the boat and extras. If there was only four Mondays in the month, the 20% remaining in the bank built up an "emergency" fund for slipping, major repairs etc. If there was any cash left on Sunday we spent it foolishly by eating out or having a few drinks as a refill was waiting on Monday morning.
Laundry was done in a bucket in the cockpit. Fill it with cold water with lots of soap powder and leave it sit over night so you will just have to rinse it the next day - once you have the soap rinsed out the dirt will be gone also. My T shirts were whiter then white and not to be ashamed off. Modern thought seems to be convinced that hot water on tap is a necessity of life - it isn't.
I was introduced to the "French" system of washing dishes - lots of liquid soap and a sponge left to air dry. Spoke to someone the other day who couldn't go sailing as their water heater was broken - thought he couldn't live without hot water.
I never used marinas because it was just beyond the budget although I had to pay for use of the town quay from time to time but one soon learned which harbours charged and which didn't. Of course, now everyone is on the band wagon and a marina berth is almost a necessity for winters but certainly not during the summer months.
You will find that life has greatly changed since the days of Pardeys with yachties especially the ladies expecting all "mod cons" while cruising. It is still possible to cruise on a small budget but you won't be able to follow the herd from marina to marina and will have to make your own amusement but you will also learn a lot about how to maintain your own yacht and equipment out of necessity. I am glad I didn't have the cash to pay others as I had to learn how to do things myself - didn't enjoy being faced with seemingly insurmountable problems but solved them eventually and look back on all the happy memories.
An article by Frankie Dixon about the cost of living/sailing in a 24 foot Eventide in YW in Dec 76 convinced me that it was possible.