Land parcel with a mortgage lien on it. Is it worth the risk?

[Grace B.]

I have an opportunity to buy a 4 acre parcel. The owner has two parcels, one is the vacant parcel and the other is his own house with 5 acres, next to each other. After title search, the 4 acre lot and the house (40 yrs old below average condition) both are under a re-financed mortgage the owner took out 10 years ago of $335,000. The house is on the market selling for $325,000 by a realtor in Jan 20. Based on the amortization table, the mortgage balance would be $286,000 by now. 

I offered $5000 for the 4 acres, before the knowledge of the mortgage lien. The estimate for the current (before virus) market (with clean title, of course ) was $18000. But now, with the mortgage lien, I will  need to hold till the house is sold and pay off the mortgage. That could be 1 yr or more. In the mean time, the market could deteriorate more. At some point if price drop so much that the owner may let the house go to foreclosure too. (worst case)

Should I buy the parcel and take the risk? 

Should I offer less ($2500 -$3000 )  and take the risk?