At those terms, that doesn't sound like a good deal at all. You have to be very leery of owner financed homes because there are many scenarios where you could lose everything.
With any owner financed scenario, one needs to verify that the seller actually owns the home free-and-clear without a mortgage. If they don't own it free-and-clear, they will need to clear enough from the down payment to do so. The reason why this is important is because if a homeowner has a lien on their home, there is nothing stopping them from pocketing your payments and refusing to pay the mortgage. I have heard of countless people that have lost everything because they fell for this. It is imperative to involve a real estate attorney when drawing up the purchase contract on owner-financing and thoroughly check the title for any liens. This is necessary in order to protect your interests rather than the seller's.
Honestly, at that monthly payment, you are far better off buying a new construction home than you would be buying a mobile home. I know of several communities where it is possible to find a home with a payment in that price range. Additionally, if you are a first-time home buyer in Texas, there are several programs available that you may qualify for. These programs could save you money over the life of the loan. You could also look into buying a lot and manufactured home directly from the dealer.
If you are interested in learning more, please contact me and I will be happy to help you. If this answer was helpful, please vote for it or nominate it for the best answer.