There are two ways you can borrow to invest in shares.
The first way is to take a loan from an existing asset, such as property. For example, say you have a home worth $1 million, with an existing loan of $500,000. It may be possible to draw down a further loan of $300,000 against your home. This $300,000 can then be invested into shares. The interest payable on the home loan may only be 3%, while the dividend return on the shares could be 4%. This then allows you to pay down the loan with the income from the shares, while at the same time enjoying the longer-term upside of your share prices increasing.
The second way to borrow to invest is through a margin loan, which is a loan that’s secured against the shares themselves. Let's say you wanted to purchase $300,000 in shares, but only had $150,000 in cash. To achieve a $300,000 portfolio, you could take out a margin loan for another $150,000. The interest on a margin loan tends to be higher than a property loan and is closer to 5% per year.