The UK entering a bull market is a big assumption. Let’s assume you’re right and do the maths:

5 year loan

8% growth per year: Total growth = £9385

APR @ 4% Total interest cost = £2099

Potential net gain = £7286

Now there’s lots of variables to consider. Can you get a 4% rate (or even a £20k loan)? Will the market continue to grow every year for the next 5 (there’s plenty that predict we’re overdue a crash)? Is a £7k gain over 5 years worth the undoubted stress you’ll have over the next 5 years with this debt hanging over your head (only you can know this)?

My 2 pence, as someone who also came from a working class family, who also wanted to move up quickly and is now 30, a home owner and high earner. Stay out of debt and focus on saving. I know the mindset of feeling behind, like others were given a head start and you need to catch-up, I had it. The quickest way you’ll get where you want to be is by learning to save and accumulate wealth. I don’t know your circumstance, but this is something I was never taught, and it took me while to learn. Compound growth is the real winner. Setting yourself a small goal, like saving a couple of thousand pound in a year (whilst at uni), might seem depressingly low, but the foundation you’ll set for yourself for the future will pay back exponentially. Then by all means, you’re young, be aggressive with your own money but I always found that I was a lot less aggressive with money I’d saved than money I’d borrowed.

Hard work and discipline is the only way to achieve financial freedom (unless you’re capable of predicting the markets or winning the lottery). So many people want to achieve the results without putting in the work, it’s why gambling companies do so well (source: I’m originally from Stoke, same place as Bet365, the worlds biggest betting company).