I hid my snake in private accommodation that had a no pets policy. A baby snake will be able to remain in a small RUB for the duration of the year. You can start snakes off in 9L RUBs. That way, you would be able to keep him/her very well hidden for that time, and try and find a place for the year afterwards that would allow pets.
I come from a family background of sneaking animals through uni. My Aunt kept stick-insects in uni halls.
If you do it properly, it's fine. But if you get a noisy animal, or have it smelly, or have it escape, that isn't fair on who you're living near. Snakes are very good for the secret pet.
Rally Useful Boxes are very good.
Here's one for £2.49 from Staples. Clear, easy to clean, and the hands lock onto the lid, which makes them very very secure. Drill small air-holes all around the top, and voila. Box is finished.
I would suggest getting a second, to use to put snake in when you're cleaning out the first, and to feed the snake in. If you want to be cost-effective, you could get the second in a larger size, so that you switch their purposes when you need to move the snake up to a bigger box.
Final point - you could be in for trouble if you have food stealers. Mice need to be kept in the freezer, and you don't need anyone finding them! An small opaque plastic tub surrounded by a really unappetising cardboard wrapper? I don't know, I didn't have food stealers.