Just so you have some info Newtomarket...
A 1-unit home is either classified as a single family residence, condominium, cooperative, manufactured home, or PUD. A townhome is just a description of how it looks & feels. Any of those can also be "attached" or "detached"... i.e. an "attached SFR", or a "detached condominium".
So when you have a single family residence, it doesn't matter if it's attached or detached, it qualifies either way (meaning there is no additional approval process).
*It doesn't sound like it's currently classified as a single family residence*
When you have a condominium, if it's attached, it needs to go through an additional review & approval process. Attached condominiums can be the toughest type of home to qualify.
A condominium can also be detached, when it is detached it is called a "site condominium" and actually is easier to approve than an attached condominium. A site condominium does not need FHA approval, and for conventional financing they are very easy to get approved too. A site condominium can look like a house, but usually has a "zero lot line" (meaning your neighbors side of their home is the wall in your sideyard).
*It sounds like worst case you have a site condominium*
This means that even if Avex won't finance you (I am not sure why they do not like site condominiums since as I said, they are very easy to approve) you should have plenty of other lenders as options.
If it's a PUD, it can also be attached or detached. PUD's never have to be approved by FHA. A detached PUD is treated just like a detached single family residence, and should not pose any difficulties with financing. An attached PUD has some additional requirements when using conventional financing, similar to an attached condominium, but not nearly as detailed.
*If you have a detached PUD, then you should have plenty of lenders offering you loan options*
I won't go into cooperatives or manufactured homes, because that information doesn't apply to your situation.