Good Deals Solve Most Problems
A good deal will solve most of your problems later on, no matter what type of real estate investing you work in. If you don't have a good deal, you're going to have trouble getting capital for it.
Rental properties may not have sufficient cash flow if the property isn't a good deal, maybe even losing you money. You may not be able to sell a property for profit if the deal isn't good. Always make sure the deal is good to ensure success with the project.