Most serious and qualified tenants are searching on the major 3rd party platforms you mentioned + realtor.com, redfin, and a few others.Apartments.com & homes.com are owned by the same company and may offer some additional marketing options.Another strategy to consider here is social media - video marketing.

Firstly, well done for persevering and trying every avenue you thought would get you the data you needed.Most would have caved earlier and handed out there hard earned cash for old, saturated leads/records from the same prominent platforms which dump them pretty much when they receive them from either 1).the same large brokers AFTER the county has listed them on the county website or, 2). from the counties themselves directly AFTER the county has listed them on there own website, or, 3). from data scrapers on Upwork/Fiverr who scrape the data from those same platforms AFTER the counties/brokers sell those platforms the data being scraped by the freelancers.Anyway, rant aside you seem to of made the same mistake i made when I first started branching out away from providing leads to my original couple of clients i got from Upwork who wanted me to scrape data from court records in FL for pre FC leads.Simply, I didn't know where to look for the information I needed in states outside of FL.FL only allows the judicial route to foreclosure so I only needed to know/find/scrape the data from Lis Pendens documents for counties they requested.

@Kevin Zmick also consider if you have an area specific advertising forum, a local facebook group,  or an area specific advertising platform you haven't tapped.  

There are many people on instagram and other platforms selling courses appearing in a certain image, selling a lifestyle that is not 100% congruent with reality and sometimes reality can strike hard and shatter perceived illusions. 

So yes, crowdfunding platforms are really just middlemen between investors and syndicators.

After all, platforms like BiggerPockets were started by investors targeting Midwest and Southern markets, where properties are much cheaper, and cash flow is often the primary focus.

Is there a platform where I can advertise a pool of mortgages for investors to buy/invest in?

I think you will find everything you need on one platform and happy to get you a free tour of the website

We were able to go from texting and emailing groups to one centralized platform where everything is MUCH more organized.

., If there are any issues with tenants or house needs maintenance, Doorvest reaches out to us by email and Doorvest also has online platform where we can keep track of all the statuses + income/expenses.