New Adult Dog around other adult dog

Question
I have had my chihuahua, Max 2.5yrs old, since he was a baby, I know I am the "pack leader" with him. My sisters friend had a 1yr old male chihuahua, John, locked up in a cage all day and was looking for a better house for him, I offered to take him in. (Max grew up around another dog and I knew he was social) They get along fine, they play and it appears they are ok around eachother, keep in mind I have had him less than 24 hours. I have two issues I am hoping you can help me with. First one is John growls at me when I correct him. (I hope its because he still isnt use to me) I am scared he will bite, what can I do to make him stop growling at me? (He is very friendly other wise and has licked me and rolled over to show his belly when we were playing.) My second issue is that neither dog is neutered, so you can imagine the affection they are showing to eachother. I do plan on getting them neutered, I just dont have the funds right now (sorry to be so graphic) but they keep liking eachothers genitals and humping eachother, I stop them, but should i be keeping them apart? Is neutering the only solution?

Answer
Neutering is a good solution, it will help John's attitude overall but it's not a magic fix or cure-all. If he gets in the habit of growling and humping, you're still going to have to break the habit. Be firm with John and he will get over it. Let him know that you are the pack leader. Maintain control over the food (make him work for ALL of it, from treats to daily feeding, make him do a trick before he gets anything), don't greet the dogs right away when you come home and if you must have them on the furniture (I know with small dogs it's hard not to!) firmly establish that they can only get up when you say so and must move when you say so.

When he growls, tell him no and isolate him for a little while (not in his crate, the crate should never be a punishment) and humping should not be tolerated. Pull him off and tell him "no". You are the boss. Chihuahuas are sassy, so you have to be firm with them or they walk all over you. But don't be loud, threatening or violent, because they are still small dogs and if you make them scared you'll have a whole new set of issues to deal with.

John is figuring out his place in the house, make sure he knows it's at the bottom and everyone will be happier. He'll be more accepting of it if he's neutered. Contact your local Humane Society or SPCA and see if they can direct you to low cost or free spay/neuter clinics. I know they have them near me so they may have them near you as well.