The magic of MLS querying can't really be done within the MLS itself because the most revealing data bubbles up when you join the for sale data with the for rent data and correlate ratios of average price in a subdivision with average rent. 

If your realtor doesn't have a sophisticated system for querying the MLS a lower-tech method is to have the agent do a full CSV dump of the MLS for SFR and send it to you after stripping out the non-public data columns. 

I'm confused about the brrr strategy, about the 70% rule. Let's say, the property is priced up for 1,00,000 & there is an estimated repair cost of 20,000. which totals the money I have to spend to be 1,20,000. 
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., With a more elaborate query for interesting markets around our NYC world 😎🌍

I'm not sure I could explain my query in the best way, but I don't mind providing more information if needed, so feel free to ask.

You can use a site like zillow or danberry or some other local brokerage to query the MLS until you figured out what niche works for you, then find a realtor. 

For those of you who develop mobile home parks, perhaps you can help me make a decision. I have an opportunity to buy a  5 acre lot zoned for mobile homes, but it is only partly developed. It has sewers, but no water....

Every time you ask a new investor questions on their very long query that makes little sense for a new investor, they snap back with "how about just sticking to answering my question the way I want."

I am not sure I understand the query about are townhomes considered multifamily?

I hope you'd find someone that can answer your query, Matt.