First Home Buyer acquired a deal but need additional advice :)

[Richer Tran]

I need help with a deal , The seller has 300k in equity in the house and owes 400k left on the house. I'll be able to get 100k down payment what should be next step?  How am i supposed to acquire this property if i'll only have 100k down payment and can I take over her payments? She wants to do a 1031 exchange to upgrade to a better property. She got the house loan at 680k and now she owes 400k left. Can anyone help me with an idea of how to make this deal happen? I've got two years so i know ill get this deal through i just need some advice!!