Those are people who have cash/credit and will lend to you if you have a good deal locked up. 

One rental(two units) just finishing renovations and spent 15-20k of my own money so saving will be easier soon instead of loading my credit card then paying it all off every month.

Use gap funding (credit lines, partners) for the down payment.

You need to build your credit.

do not use a line of credit for a down payment. 

If you have nothing, and make nothing, you declare bankruptcy, wreck your credit and try to go back to renting.

If the property were owner-occupied, would I only receive credit for one rental unit's income, while the non-conforming basement income wouldn't count?

It's likely a scam anytime they sound like AI or the grammar is weird or they use the word "kindly", if they ask for you to respond to them off-platform, if they say their employer will pay for it, if they ask if the dates they've specified are still open (when they can clearly see they are open on your calendar), if they ask for a video of your property (they probably want to set up a duplicate listing with your photos and video and scam others out of money), or if they want a long term booking and they have just joined the platform and have no reviews (could have been evicted from somewhere else, and hope a newbie will let them in with no background check, they'll end up not paying or credit card is bad).  

Consult Real Estate Attorneys: Attorneys specializing in real estate often have connections with private lenders and can provide referrals based on your specific needs.Engage Mortgage Brokers: These professionals have access to a variety of lending sources and can help identify financing options that align with your objectives.Local Banks and Credit Unions: Establishing relationships with local financial institutions can lead to personalized financing solutions and potential leverage opportunities.By focusing on these qualities and avenues, you can find a business broker and financing options that align with your goals. 

Plus, if you aren't able to get approved with what you've got now in terms of savings, credit, etc. you can learn on what you need to qualify so you know what to be working towards.