Financial questions that need an answer

to buy our trailer for45000 dollars does any one know of any drawbacks to doing this or can some one give advise on what we might be healthy to ask for like a lower price and how we can make this a good investment for ourselves and our 3 grandchildren were raising. we rent the lot for 350.00 a month and the rent is 1000.00 for the first year then it goes down to 800.00 but that would mean it wil take awhile to pay off i guess that dont matter when we have a 5,6,7 year old,two with adhd and all with emotional problems, and our own 14 year old we just want stablility for them we want them to know they will always have a home.