Grant Cardone says "Don't buy real estate on a budget"

[Damon D.]

Still very new to the game, but I'm starting to look around for multifamily / small apartment properties. I'm not advanced enough yet to try to cobble together a deal with other investors (at least, I don't think I am) so I am of course doing backwards math here, saying "well, I can invest X amount of dollar, so that means I should be looking for roughly (X)5 priced properties considering a 20% down payment." 

Is this really the wrong way to think? My instinct is that this is the actual, logical way to go about doing the early math: figure out what you can afford and try to find the best deal within that range.

Am I doing it wrong?