Gonzo, you've answered the question very well, that in some cases a townhome sale would be considered by a condo buyer, AND be competitvie to subject, in this case, the poor condition of subject property, lack of basic amenities such as guest parking, and lack of eligable FHA financing , and design/appeal make SUPERIOR townhome sales not competitive. Just because a sale exists in the market does not make it a comp. And yes, I have used townhome comps in condo reports and vice versa, but there has to be a reasonable equivalency among property types, and price points. If every townhome is 50 k higher than subject , and there are townhouse listings avail , and subject is in contract, one has to assume that the buyer chose a condo because townhomes were out of price range (and that typical buyers would do the same).
Adjusting a superior townhome form a diff price point down to match an inferior subject is ludicrous and can be easily be seen in review if anything happens with apprasisal later.
If townhomes are only 20 k higher, and a range of similar condos sell for more than subject, then the townhomes need a smaller adjustment and perhaps ame buyer profitle/typically motivated buyer might look at both.
Yes, there are lists of AMC's, a few are free, I think the TAVMA website has one, most of the more extensive lists are a $ charge (there's one forum member who prepars a list if I get the name later will PM you), the paid lists are worth it esp when starting out. .There is a lot of work out there now so a good time to apply. Apply to a number, because that is the only way to pick and chose...which pay better fees, (higher ), which don't pressure for value or have ridiculous turn times etc.
When you have a number of clients, you can drop the bad ones and certainly this client sounds bad. They are pressuring you for value like I have not heard of since the mtge broker days. You should not be talking to the realtor at this point, if they bother you again, tell them you already have their input, they are not your client and you won't be speaking with them again on the assignment.
Ask whoever it is pressuring iou on the AMC /client side to please put their reqeust in writing from now on regarding changing the report. (if it has all been on the phone). (so you have a record if you need it later). Be professional , but tell them you have all the input you need and now have to be finish the appraisal.
If you don't use townhome comps, explain why in the report, that you considered them, but because of poor condition of subject etc, they were not competitive as sales (or use an ugly, run down townhome comp if one is avail)
Hand the appraisal in and there's a chance if it's below SC price this client may drop you, they will be doing you a favor if that happens, as you need to get other clients ASAP, even if they don't drop you. If down the road you can manage to get the cert gen license you'd have more options, going for SRA gives you more options as well. But even now, you can get diff/better clients.
Good luck and get it out and over with.