You'd own the debt, not the house. The borrower owns the house and keeps owning it as long as they pay. You hold the note, which is their written promise to pay, and the mortgage or deed of trust, which is the lien letting you force a sale of the property if they stop.
That answers the roof question in a way that feels strange the first time. The roof is the borrower's problem. You don't pay for it, you don't approve it, you don't hear about it. Your exposure is indirect. A borrower facing a $14,000 roof on a house they owe $95,000 on may prioritize the roof over the mortgage payment, or may not fix it at all and let the collateral degrade. Neither gives you a bill. Both can eventually cost you, because if you ever do have to foreclose, the house you take back is the house as it actually is.
The one thing you can and should control is hazard insurance. Your position as lienholder normally entitles you to be named on the policy so you get notice if it lapses, and most servicers monitor that. If the policy does lapse, servicers typically place forced coverage and add the cost to the loan, which is expensive for the borrower and a common reason a paying borrower starts missing.
Since you know this house, you're in an unusual spot. Most note buyers order a broker price opinion, which is a licensed agent's drive-by valuation, usually somewhere around $100 to $200. You already know what's behind the walls, which is worth more than that report. What you don't know is the borrower, and on performing paper the borrower is the asset. Ask the seller for the pay history and how the loan was underwritten when it was made.