Hello Ian,
Using a Heloc to purchase your next investment is not a problem. Some lenders allow you to go up to 90% combined loan to value meaning whatever your balance on your first mortgage is plus the equity loan can go up to 90% of your homes value. Example if you owe 300k and your home is valued at 600k you can only borrow up to 90% of the 600k value. 540k is 90% of 600k. If your balance is 300k then that means you can take a line of credit of about 240k on your property. Depending on the type of Heloc you get its interest only payment for the first 3, 5 or 10 years then the remaining time will be a payment of principal and interest.
Heloc is a full documentation loan meaning that they will verify your income and credit. Just because you may have enough equity to go up to 240k doesn't mean you will be able to access it all because what if you can only qualify for 100k. The next factor is since you are looking to use that towards a down payment for your next investment you will need at least 20-25% down payment. Make sure to do your due diligence when acquiring your next property as you will need to make sure the rents can cover your mortgage payment. Any negative balance will go against your DTI when qualifying for the investment loan. Lender only uses 75% of your rents to offset the mortgage payment with taxes and insurance.
Take aways here are to make sure you have a high active income to be able to use this strategy. Not sure what market you are in but if its in an expensive market you will need a really high income to proceed. Make sure to plan ahead and speak to an investor friendly lender that can help you look ahead at potential roadblocks and how to avoid them or overcome them before getting your self into a sticky situation.
@Albert Bui @Matthew Kwan