A shed is essential for those showery days and cold days in winter, also to get shade in summer. My shed has no windows but double doors which makes it open to sit in and meditate. Do not know where you live but I looked on Free Recycle for a shed (UK). www.freerecycling.co.uk
My allotment was like yours covered in grass and brambles but now three years on most of it is dug but the tussle with weeds never ends. I had a lazy week last week so I have some hard work ahead over this weekend. I will also be planting out my leeks which I grow in large pots until I have space to plant them and for the cabbage white butterflies some kale and cabages.... also grown in pots in a at home.
blessings on your progress.