I have previously helped some family members search and buy properties but I have yet to close on my own.

Google / Youtube BiggerPockets Podcast Mobile Home Parks.

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Thank you @Roberto Torres I'm in the process of searching for my very first property in the philadelphia market.

I also do some googling and check out Facebook or anything where people tend to let their guard down.

"Ohh I need backlinks, ohh I need content ohh I need citation".Wrong.It is not just about having what you need to have for google to love you.. you need to be BETTER than the BEST site in your market. 

I am thinking of using investorcarrot to generate leads, but I don't want to put the money into it if I still have to pay for facebook ads and google ads.

I live in Fairhaven so I would google "fairhaven online assessors database"........ 

Is there a comparable Website for searching “Homes for Sale by Owner” as the MLS for Agency Listings?

That's not strong enough, btw.Meanwhile,  put your money in high apy savings accounts (Google it).