“I’m a First Time Buyer, my Girlfriend will be living with me. What do I need to consider in the home buying process?”
Congratulations! Buying your first home is really exciting. If you plan on having your girlfriend living with you there are several things you need to figure out before hand.
First, you need to clarify up front whether you are buying the home together or if you are buying the home and she is living with you. This can have a lot of implications later on the down the road. If you guys end up splitting up it will have a large impact on what happens to the home if you bought it together versus just you buying it on your own. If she is legally on title she has just as much right to the home as you. If you are the sole owner then you can ask her to leave any time.
You’d be able to buy a larger home if you both buy it together because then you can use both your salaries for getting approved for a larger mortgage. From the wording of your question I would guess that the plan is your girlfriend will not be contributing to the downpayment and will just be living with you at the home you own.
Second, will she be contributing to the mortgage payments? If she is contributing to helping build equity in the home then she may be entitled to money if you break up and she moves out. To learn more about specifics of how you could be affected legally then you should speak to a lawyer. These laws can change at any time. For instance, without children, right now it would take three years of living together before being considered common-law couples. That could change though so make sure you speak to a lawyer to find out all the legal implications.
It’s also important to consider the future. Is this someone you think you will be with long term and having children with? If so you will want to consider where the home is located to help her as well. What is the commute to her work? Is it in an area with good schools in case you have children together?
Buying a home is a large step to take in your life. So is having your significant other living with you. If you think this is someone you may spend a long time with then you may want to let her have some input on what home you buy. Speak to a lawyer before hand though to figure out the best way to set it up so that your financial situation is protected as much as possible. 
If you have a question you’d like answered let me know and I will get you an answer!