How to get Real Estate Comp pricing information in Mexico

I have asked around and it seems that there are no real estate comps (a compilation of recent selling prices in the area you are searching for a home or condo) in Mexico. On top of that, the market is pretty illiquid so asking prices are not really a good indicator of actual selling prices, either. The only reliable indicator of selling prices that I have found is preventas (posted prices by the condo builder for condos under construction -- these are discounted somewhat the earlier you buy in) which are probably a good rough indicator of what condos in the same area are worth. As far as houses go, there doesn't seem to be anything more than just compiling asking prices.

Any ideas on getting pricing information for a local market? I live in a major metro (Guadalajara). But I assume the same issue applies everywhere in Mexico, especially to non-condos. I am also wondering if most offers for homes are lowball offers since that would seem to be logical for a market with so little public information.