It IS generally customary and acceptable, with proper written notice, to change where a payment is to be sent, and update management contact info, but in order to change "material" terms such as method of payment, or amount of late fee, or virtually anything else specified in the original, you need to bilaterally agree to, and sign, a new agreement.

I would like a bi-lateral exchange of information.Any software out there that can do this?

Based only on the info you provided, sure it's legal...you have a bi-lateral contract which you are uni-laterally asking to cancel.

Anything in an optionagreement could be in a sale contract and vice versa.The legal nature of the two are not the same, one is unilateral the other bilateral, but if there are no penalties for compliance, there is no effective or enforecable difference.There are risks of death, divorce, bankruptcy, loss of income, future claims to the property, liens, judgments, loss from disasters and insured perils, failure to maintain the collateral, failure to pay taxes, title issues and others with any seller finance transaction, for that matter, any financed transaction.

@Chad Clanton  An Addendum is a bi-lateral agreed alteration of the original contract to which it refers

I was told somewhere that it is bilateral.

If you could get a contract in place with the original seller, then you could attempt to wholesale the deal to a new buyer without the need for a real estate agent since you would have obtained equitable interest by virtue of the fully executed bi-lateral contract.However, if the wholesaler will not allow you to go into contract directly with the original seller (or the wholesaler demands his/her fee to assign his contract to you prior to closing to which you would have to come out of pocket a significant amount of cash with no guarantee the deal would close which is typically not a good idea), you would need a real estate license to avoid the appearance of brokering the deal (practicing real estate agent without a license).

So we have a bilateral sale agreement on a foreclosure that has no contingency for selling my current house.

canceling a bilateral contract unilaterally seems like a perfect solution!

The main point is that a lease is a Bi-Lateral contract.