A portfolio loan should be viewed like an overdraft in a business. Short term movements in amounts drawn within the limit then paid back within a short period. A portfolio loan would suit a flipper who is trading property within a 12 months period. Investors who hold, as Terry said should be opting for a term loan.
All investors should be calculating their investments with debt based on a principal and interest repayment basis at an average interest rate of say 8%. Unfortunately most investments would not make sense under these circumstances.
I lend money in Melbourne to real estate investors who fix and flip or fix and hold residential real estate properties. At times I can lend 100% of costs to buy the property and renovate. I am able to do this by taking a view on the after repair value of the property and when the property + renovation costs is purchased at a discount to after repair value of at least 35% (ie 65% LVR ). Banks will only lend on an "as is" basis which means you usually can leverage to the lower of 1) purchase + building costs; or 2 ) on completion value. Each deal is subject to approval.
No money down does not mean "I have no money at all" and "I don't have experience". We look heavily at the borrower, their ability and track record and also a buffer to absorb financial shocks if things go wrong. If the borrower is deficient in these senses, we recommend them teaming up with people who have the missing components. We are less concerned with financial statements and are more concerned with the security and the potential of the borrower.
To reiterate what Terry stated above, can you service the additional loan with your current income – obviously there will be no additional income from the vacant land. Further, what are your plans with vacant block over time?