Maybe go to the furniture stores and as a shop assistant for some ideas.

Mom148397 – I would love to see pics of you have any of what you are talking about? TIA

using the existing cot bases put small lock down castors on each base frame and place on floor .safe distance if falling out and when older use the cot sides and make proper beds without the castors . We have used this idea for 9 kids and it works . can slide the made up bases under our q bed out of the way ,can even transport to Mas house when needed !!!!! only a little DIY needed

A good idea is to go to furniture stores and look at the floor stock and take measurements of beds and bedrooms with storage. It will also help with giving you plenty of ideas for your own home and bedrooms.

We went for a bed with a trundle. The bed itself is not too high and the trundle rolls away nicely during the day to leave space in the room for them to play

When your twins are just moving out of their cots I can imagine they’re not ready to go in a bunk bed yet. You can get great storage systems for under the bed though.

You can get low profile bunks which aren’t very high off the floor and they have sides all around the top for safety.

We got an ikea junior bed which is longer than a cot, this is a great space saver but was an expensive option although we got the bed base second hand, just the linen and mattress were expensive, you only have the ikea option

My daughter has this one, that we bought in Harvey Norman 4 years ago. Her bedroom is quite small. The bunk bed makes the best use of the space available.
The drawers on the stair are very handy!!