I would like to retain this house and turn it into a mid-term or long-term furnished rental.I would like to move out of that house and into a bigger primary residence which would likely be a $750-850k purchase price.

You retain ownership and responsibility for the property. 

Talk to a lender or read some online material to learn how to do it quickly and wisely.

You'll need the tenant to sign it as well.That said, if you want to retain the tenant there are some things you should consider before pushing the rent way up in one go. 

And it needs to be in your area if you're going for material participation.

The previous owner was handyman to the property(as I will also be) so I would think maint# is likely Material only.

All tactics to save time & money.If this advice seems unprofessional you can send me a $10,000 retainer (first of many) and we'll go fight the bad guys, win justice and protect the American Way!!!

IE - they're stringing you along to get exposure to deal flow, and they're not making any tangible or material commitments to being your financial partner, unless it's an absolutely incredible deal that they cannot afford to miss out on.

I recommend building your elevator pitch (30 seconds or less), your uber presentation (five minutes), and your listing presentation (up to 30 minutes with supporting materials).

Lending Provide a copy of the contract to your lender so they have the material terms of the agreement.