this is not investment advice

It certainly looks like investment advice!

That's for the lawyerly among us.

Let's say I have $1K at Fidelity. Which fund should I buy (long-term growth)?

(This comment pertains to Vanguard funds cause I don't know Fidelity). For long term growth you'd likely want either all-stock or a balanced fund, with the lowest costs possible. Unfortunately, funds like Vanguard 500 Index Admiral Shares (cost ratio of 0.05%) have a min of $10k, and 500 Index Investor Shares (cost ratio of 0.16%) has a min of $3k.

So below $10k you're not going to get the best expense ratio, and many of Vanguard's funds have a min of $3k so you can't buy the Vanguard LifeStrategy class or 500 Index fund either. You CAN however buy a Vanguard Target Retirement fund ($1k min and ~0.12-0.16 expense ratio). You don't have to use it for retirement -- you can invest in it just like any other fund, and if you choose a longer horizon the fund will be 90/10 stock/bond or 80/20 stock/bond biased.

With 1k you should hold it in cash unless you have some ability to get shares through a special program (employer, trade organization, club, etc).

With 2500 you should go FSTMX.

(Don't take investment advice, including this, from strangers on the internet)

By loans you mean the mortgage too? Pay that off first?

In Australia you could pay off your mortgage then refinance in a brand new loan to buy investments. The interest you pay on THAT loan is income tax deductible.

Mortgages are a special case because the debt is usually tax-subsidized, and depending on the state, one effectively has the option of giving the house to the bank in lieu of paying the remaining balance.

That is a difference in the US. In UK/Australia you pay the mortgage from your post-tax salary.

Encouraging some people in Australia to perversely rent their house out and go and rent a similar house (sometimes identical apartment in same block!) from someone else, in order to get the interest offset against tax.

In the UK it is even worse, as you can only claim 20% of the interest cost on an investment property even if you are paying 40% tax on the rental income (!!)