If they don't pay willingly, what are my options? 

Typically this means they will take longer to close, may not have all the information for the companies they work with, and most hard money brokers get their money by taking an existing product and adding extra points to pay their fee.What is your investor success rate?

If worse comes to worse and I need to get a judgement against the tenant and co-signer(s) can I force them to pay?!?

Are buyers struggling to accept paying their agent as a new structure? 

I'd pay it & chalk it up to lesson learned.

The median closed sales price in July 2020 was $329,000, as compared to $275,000 last July and $213,000 back in 2017, according to the Ulster County MLS.

Purchase price: $185,000 Cash invested: $35,000 Sale price: $671,000This was our 3rd home.

Quote from @DR Rearwin: Be aware that if you purchase a property as your principal residence, and later convert it to a rental, the lender may have the option of calling your loan and making you pay it all back immediately, since you have changed the use of the property.I never knew that.

I've been toying with the idea of adding an ISA to my sales business.

So many things wrong with all this.First don't pay for this.