Upon prior written notice to Seller, Buyer's rights and obligations hereunder shall be assignable to any tenant in common investors, joint ventures, affiliate or subsidiary or qualified intermediary without Seller's prior written consent.

Because of such reliance made, a borrower can not simply "assign" their obligation to that lender without the consent of that lender. 

Lacks the intent to purchase, consider it this way, (just making a point) say I give you nominal consideration and enter into a contract to date your daughter, and your daughter gives her consent agreeing to date me, and you consent as well.

Because the property is owned by my sister I'm reluctant to give out specifics just yet w/o her consent and because I really can't market it myself if not owned by me.

They are running a business ourt of the property, subleasing without my consent...

Borrower shall occupy, establish, and use the Property as Borrower's principal residence within 60 days after the execution of this Security Instrument and shall continue to occupy the Property as Borrower's principal residence for at least one year after the date of occupancy, unless Lender otherwise agrees in writing, which consent shall not be unreasonably withheld, or unless extenuating circumstances exist which are beyond Borrower's control.

However, the license law does provide that a licensee can be disciplined for offering property for sale without the knowledge and consent of the owner or the owner’s authorized agent, or on terms other than those authorized by the owner or the owner’s authorized agent.

There is another guy living in the unit without my consent, and honestly he seems like a criminal.

Make no major changes to the premise, such as painting, rebuilding, removing or repairing without the Landlord’s consent.

You shouldn't have an issue assigning the contract, it would be better to have consent of the seller to assign but you don't need to indicate the higher price.