There are too many variables to determine any reliable statistical data on the matter.

Also, I not sure how to market to end buyer with so many variables such as having too many end buyers inspect the property I mean this can end up being a burden on the seller and the tenants.

There are 4 variables, time or duration, interest rate, present value and future value, enter any three and solve for the fourth. 

That is encouraging news and although it is a variable rate it is pretty unlikely to shoot up over night ( I hope).

I am busy trying to learn so many things that it might not be a good idea to add another variable in to the mix.

Year 3 is going to be $16,000 x 5%....etc.At this point, I have more stable cash flow, so I think I would either ask for variable payments with the minimum being 'interest only', or try to extend the payment period, but you may find that difficult given the specter of higher interest rates in the future.In another instance, I am working with an investor to complete a flip.

Lots of variables there that may make it all moot, including whether or not the OP's seller will really sell.

I thought that would be much quicker than trying to figure out a spread sheet that could compute all the variables, especially the snowball effect.

I'm using all the money I get out of this house to re invest into real estate or other investment avenues.I guess I'm a little nervous about the HELOC because its variable tied to prime (which is low now).

Sure would be nice to have a clear cut answer to that, but there is not.There are too many variables involved, remaing term, credit, seasoning and proven payment history, collateral, loan to value, property condition and the details of the contract including the security assignement and foreclsoure process.Best to get bids, and look in your area for other investors, including those who buy RE, your best deal might well be from a local individual looking for a good investment.