Maybe I missed this somewhere in the OP or in the comments, but what is your dad's friend's reasoning for owning your own home outright before you start to buy rental properties? Even buying your own home before starting to invest isn't really a "must-do" to-do item in my opinion, it all depends on your personal situation. If you live in an area that you and your family like and you don't forsee any reason to move in the next 5+ years (job changes, move closer to family, etc) then it might be a good idea to stop putting rent money in someone else's pocket and start building your own equity, but it's really a personal decision based on your individual circumstances.
As far as paying off your house (assuming you do buy one) before buying an investment property, unless it's a personal "comfort factor" for you, I think it's a waste of your exra money and almost ten years of NOT being invested in anything given how low mortgage rates are. I see how $3,000/year is low "dollar-wise," but 10% return is still higher than any current mortage rate on primary residences. If you put $30,000 in the bank and earned a 10% return on it over the year, anyone with a pulse would say that's an awesome return, so looking at it from an ROI stanpoint, if you make early mortgage payments on a 5% loan, you've only created a 5% ROI (in other words now you've tied up $30,000 for a year to only earn $1,500), as opposed to the 10%/$3,000 return you could earn elsewher in the market. Choosing the 10% ROI option is clearly more logical, so to me it does not make sense to tie up all of your money in a liability (your primary residence is a liability if you only live there and generate no income from it), unless having a paid off house is just something that makes you sleep better at night.
