So, what happens if your relationship doesn't work out? Then you are on the hook for a portion of the mortgage until he can sell... and have to rent. Sounds dicey give problems as of late. 

Also, do you really want to buy "his ex wife's house". If you do decide to purchase together, wouldn't you rather start fresh in a different place of your own?

Sell it and let him get on his feet.  Don't hook up anything financial with him.  He needs to prove he can contribute fairly to your future on his own.  If you were to buy the house, it would always be the marital home in everyone's mind, no overcoming that unless you do a total gut and that costs money.  

Its not a good sign that he throws throwing you out in your face either.  I might move out on my own for a while and let the dust settle as he gets back on his feet.  Its not your problem if he can't make it without you.  Do you really want to take care of him and his kid until he ages out?  What will that do to your retirement?  

Coming to a real estate buy as equal partners financially would be the best scenario.  That way you both have leverage to use in your battles with each other.  

I am a firm believer that when a couple desire to start living together, a fresh start in a fresh 'our' house is necessary.

Being the man can not afford this current home on his own and has threatened to boot you when the mood strikes him, I wouldn't be considering buying any house with him. You've been with the guy a year. 

Check out the blogs of futurobrillante99. Or perhaps she will see your post. She purchased a home with a guy she thought she had a future with very early in their relationship. 

Buy an "ours" house if there's a future with this relationship. Speaking from the experience of living in the house that DH and BM bought together, it never truly feels like "home" no matter how many walls you change or how much paint you slap on them. 

However, I strongly suggest getting your own place and letting your partner work out his finances and housing with his ex. Being threatened with homelessness is a HUGE red flag for the relationship.

If you want a house buy a new one.  Not the EX’s house.  He can’t afford it, then he has to sell.  What you do after that house is sold is up to you.  Or what deal you two come to about a new house, like,he can not throw you out ! 

How you do financially, how much you pay a month, how much he pays a month !  For house, food, ect 

I personally would never buy a house with a man to whom I was not married unless the relationship was rock solid and I had a well written tenancy-in-common agreement.  I would not consider buying a house with a man who had threatened to kick me out of my home.  In all honesty, I would not even be with a man who had threatened to kick me out.  

You seem to be opposed to renting, but renting could be your best option.  With the increase this year in the standard deduction, some of the tax benefits of owning have gone away.  In many areas, it's cheaper to rent than to own, and appreciation is not guaranteed.  If you want to own a home and can swing it on your own, let him sell his house and buy a different one.  

Move out, get your own place, let him sell his house and he has the option to move in with you. Then you will have all the power. But you would never threaten to kick him out because you aren’t as cruel as he is. Always make sure you hold all the cards.

Renting gives you the option to walk away relatively easy. Buying a house with this guy will be like hanging an anchor to his dysfunctional past around your neck.  He threatens to kick you out? What an @$$! Make a clean break from this jerk when the house sells or even before.  

Oh HELL no.

I'm in a position sort of like this now except I am the one still in the marital home. House is going on the market and we are getting a new house together. However, our relationship IS rock solid, we are engaged. This is the most amazing relationship I've ever been in and every single day is a reaffirmation of how good our relationship is. The 'step' problems we have are mainly with crazy exes and the usual sort of drama that comes with kids - but we have three good kids between us.

 And still... I'm a bit nervous about going into a major financial committment with this man - and I SHOULD be. 

No way you should be entering into a financial agreement with a guy who threatens to kick you out once - never mind as a semi-regular occurrence. That's not the way you treat a partner. 

Personally I wouldn't be able to respect a man that threatens me with eviction. I would not commit to a mortgage. At best stay renting because you can always walk away from that but to purchase a house and one that he shared with his Ex is a h@ll no.

You want to start anew and create a space with new memories. Also the fact that you are having issues with his kid is another red flag so listen to your gut and don't commit yourself to a house with this man.

Definitely sell. I moved into the house my SO lived in with Crazy (BM), and I hate living there. It's just a rental, but still. It feels like his, and not ours. I can't wait to start fresh. And once during a bad fight he threatened to kick me out. This was almost 2 years ago and never since (we hashed it out and that problem is now fixed, including the fact that he doesn't get to threaten to kick me out). It's a terrible feeling.

they should sell the home.. he should buy or rent something he can afford.  If it's a rental and you are also renting.. perhaps you may consider being on the lease with him.. but when he is making threats?  Nope.. sounds like a grand opportunity for you to go find your own place and take a bit of a step back.