Ah, well in that case, if the business plan means that the rents have to double to make a decent profit, then obviously the landlord will evict the tenant and sell the house. They may not sell at the top of the market, but it's better than being trapped in a loss making concern. What will happen to the tenant is anyone's guess.
The landlord sells into a falling market and if new to the job they could well be in negative equity, tricky balance for some.
Sometimes a decent tenant could be an asset if you're scraping up deals for your pension.