Unlike buyers who can cancel and forfeit their escrow deposit (or not, if exercising a contingency), the seller doesn't have the right to back out. 

Certainly the seller has a number in mind otherwise just offer 1/2 of what Zillow says it’s worth with an inspection contingency. 

So I would go in with my best offer and no contingencies.

She has two young children, one of which is on the autism spectrum, so moving twice would be difficult for them.I'd like to help out and purchase a place that they like, and then once they close on their sale, have them purchase the home from me.Market where they want to buy is super hot, so a contingent offer won't work.

You could also write into the contract of your next duplex that it is contingent upon you selling your single-family home. 

-and to answer your last question, I don’t have a current funding source if I can’t sell the house but in my purchase and sale agreement I would use a 10 day contingency that I could use to back out of a deal if I could not find a buyer because if the house hasn’t been sold in ten days.

Few recent sales.....2621 W 24th - 2 units - Contingent from $500k2610 W 24th - 2 units - Sold $500k 3/17/21I personally think these prices are over valued and would not recommend them for investors to long term hold, I forecast the rents to be under/around $3000 for the above buildings (both sold vacant). 

Also, remember that almost everything in a "bid" or contract is negotiable so you can go under contract with an inspection contingency and have the ability to back out if unsatisfactory.

Why might the sellers ask for this contingency and has anyone been able to void on HOA? 

All cash, close quickly, zero contingencies other than clear title which is how I've operated the past 10 years or so.