Having owned three aircraft on my own, I would advise as strongly as possible to share ownership with someone else. You NEED someone else to share your experiences, worries and problems - not always of a financial kind.
Also buy an aircraft that you can some day sell and get maintained, think very carefully about permit aircraft unless you are involved in the building yourself. Don't forget that an aircraft is being sold for a reason and neither the seller (nor you when you sell) will mention it's bad points.