Replace or have roof certification prior to selling multifamily?

[Nick Clurman]

I'm recruiting opinions on how to address a home's roof prior to selling. The home in question is a two-family, valued between 350-400k. The roof is likely twenty years old and shows signs of age on close inspection. The roof looks pretty good to the lay man's eye.

It has asphalt shingles, that are the dimensional type (fairly high end for the era of installation). I've had no fewer than 4 roofing companies out to give me an estimate. They all want to completely replace the roof. I know because there is only one roof layer, I have the option to do an overlay roof. The overlay is tempting because it will save me a few grand, versus a complete tear off. Most recently I had a roof certification company to inspect the roof. Based on the feed-back I got from the prior roofing companies, I had little hope that it would be certifiable. However,they will certify it for 2 years after performing $400 in repairs.
Should I....A) Tear off old roof and install brand new $14,000 roof? 6-8 week market delay.B) Do an overlay roof for 11,000? 4-8 week market delay.C) Have it certified by Roof Doctors who will warranty it for two year for $600? No delay. I'm told FHA will lend on home with this Certification.
Thank you in advance for any constructive opinions.