Unfortunately there are no home brain scanners. MRI machines are extremely expensive, which is why waiting times to have scans done can get long (even in large hospitals in wealthy cities). If they were ten-a-penny, you wouldn't have to wait 3-6 months for a scan to see if your cancer is back - they'd just do them weekly.
If you want to track your brain architecture over time, I honestly think tracking your performance is a good proxy way of doing so. Try setting up some ways to quantify working memory, verbal fluency, productivity (so focus), and so on. If certain areas of cognitive performance develop rapidly, then you can be confident that the relevant area of the brain is undergoing some significant structural changes.
I hope that helps anyway. I wish I could link you to a nice, reliable, safe home brain scanner!