I could be wrong as I'm new to the game but ime, the bank account must also be able to to cover the cost of the hideouts rent.

I had upgraded my laundering pool very fast and resulted in draining my bank to below the value of my first rental property.. this resulted in the property door being locked. I lock picked my way inside to find that all my furnishings and all my items had been wiped from the property. I am lucky I had only stored less than 3k worth of items inside.

That repo man Byers wants his money!

My exposition factor was fairly high when this happened and one of my dealers had been arrested but I was only notified of their arrest after I bailed them out, so it could have been DEA related gamebug situation.. although I dont think DEA raids result in the property door being locked. So I'm fairly certain it was a result of not being able to cover the hideout rental price. Anyway, I suppose that's why it would be called a Rental hideout. Make sure to keep that bank value up.