In 2 years time I'll have a TM and can charge the big money.
But you'll still be "living in a very economically diverse area, where people are struggling for money".
So why can't you charge the higher fee now? You don't need a tm to charge big money.
The price is all in your head. If you can get £35 for a room, then you can probably get £45, and if you can get £45..... you can probably get £60 etc. What you need is a change of mindset not a tm.
Why do people limit themselves to their own locality, if it's grim where you are spread further a field into slightly more affluent areas, you go where the market is that you want to target.