First off, you should know that getting a loan as a foreigner in Mexico is quite difficult—most traditional lending options aren’t available, so you’ll likely have to explore alternative financing or fund the construction yourself.When it comes to managing the property as a short-term rental, you'll need to decide whether you want to open a small company in Mexico.

The main investor did quite well on the deal too.

I've been anon lurking for years but am quite keen to roll up my sleeves to learn more.

Just get the loan with the co-signer then quit claim it later to get them off.

Yes, this is quite a common practice for professional PM companies.

I have heard it’s cooled down quite a bit and assessing if it’s still a worthwhile option to consider as a market for str or even mtr? 

However, if you're set on managing it yourself there's plenty of websites and apps you can utilize for rent collection.Some may or may not include messaging for requests such a repairs or maintenance, but if you're looking for rent collection there's quite a few options on the market that are affordable.

Do not just quit claim deed your property!

I don’t know what the rent is or how much longer he has on the lease, but $5k at a little bit extra every month would take quite awhile to make up.

Well, if the FMV of the house is at or near $300k based on reasonable comps, and there's no legitimate benefit to the client's offer (i.e. all cash, fast closing, no contingency, whatever), I'd probably quit working with them because there's really little to gain working with cheapskates and bums who just want to steal other people's property.