Follow ups are key as the average person takes 3-5 touches before picking up the phone to respond.When you're getting started and planning out your campaign, there are two things that you should ask yourself that will help you determine your mailing quantity:1) Your budget2) Your ability to handle the callsIt might help you answer these questions if you had an idea on what to expect in respect to the response rates.

The secret, for me at least, is quality over quantity.

Quality/consistency of cash flow should also be considered, not just quantity.

Use your time on the MLS to learn the market you're investing in, but opt for quantity over quality.

RE: directly reaching out to human resources department for internship@Ralph C. it's because achieving the end goal is usually easier when there is an introduction from a known quantity.

Even if the new tenant checks out fine, they are still more of an unknown quantity than the one who has a mulit-year track record of being a good tenant. 

https://www.sherwin-williams.com/document/PDS/en/035777440230/Emerald, ProMar 400 and Harmony, same thing as above.https://www.sherwin-williams.com/architects-specifiers-designers/products/interior-paint-coatings/paint-coatings-interior#facet:&productBeginIndex:27&orderBy:&pageView:grid&minPrice:&maxPrice:&pageSize:9&

If retail is something that you want to pursue, increasing quality ($ of house) and quantity (# of transactions) gets you there. 

On the risk mitigation front, no matter the market or how strong it looks, I always assume that it will crash the day after I close escrow, and if that would put me into serious financial trouble, I'm not closing ... and as your example on PHX and your buddy's 4-plexes illustrates, cash flow is not some magic wand that single handedly makes you immune from any and all risks (as some newbies seem to think), though it is an important part of the equation, and the quality of that cash flow is every bit as important as the quantity.

I suggest you do a quantity take off estimate to give you a better idea of cost.