An alternative condominium means another condominium that you could choose from. The condominium alternative means the choice of using/having a condominium. Examples: "An alternative condominium you could look at is the one at 55 Queen Street. You might like that one better" "When I was looking for a place to live I had to choose between a house and a condominium. The condominium alternative seemed worse to me because I would not own the lot of land but only the structure. So I chose to buy a house instead."

In "condominium alternative" alternative is a noun, not an adjective and used to describe something than can be substituted for something else. So "Summerwind" (whatever it is) has the features of condos but is not the same (or the marketing people want you to think it's not the same) and if you want to buy a condo, you could also consider this. Another example - soy is a milk alternative for people who are vegan or lactose-intolerant.

You are quite right. The adjective does come before the noun. The two sentences are different grammatically because they have different meanings. alternative condominium = adjective + noun condominium alternative = noun + noun In the phrase 'an alternative condominium' , the word 'alternative' is the adjective, and 'condominium' is the noun. In the phrase 'a condominium alternative', the word 'alternative' is the noun. The word 'condominium' gives us more information about what kind of alternative it is. When a person is deciding where to live, they have various options - for example, they might have a 'house alternative' or a 'condominium alternative'. Noun+noun compounds are very common in English. The second noun tells you what the thing actually is, and the first gives you more information about it. For example, 'a winter jacket' is a jacket which you wear in winter.

Yes, there could be a difference in meaning.