Some more information: We currently own three other rental units (all are cash flow positive). Our credit scores are excellent (760+) and our monthly DISCRETIONARY income after all other fixed expenses is ~$8,000.
Cash flow isn't the issue for us. Right now it is down payment because I just finished buying and renovating another two-flat that we purchased in March.
The building we want to buy would be cash flow positive minus approximately $36,000 that I would be investing in order to upgrade some features [mainly kitchens ($15,000), HVAC ($10,000), and build a new garage ($11,000)].
I know that I can always wait half a year and have the savings to put 20% down on a building, but I have the chance to buy a cash flow positive building right now and would rather not miss the chance. We also have the ability to take out a HELOC on the other three units, but would prefer not to.