It will not amount to 0.25% to rate, more like 0.25% to discount points.Here is Fannie Mae's fact sheet thingie.

My architect got the files at the beginning and fixed the problem cause the seller said that he is not paying anything that needs a fix cause he sells in a big price discount ( 23600€ for both apts).

While landlords hate to drop rents, and resist it like the plague, make no mistake that during a downturn your income will fall even if you don't drop rents.Vacancies will increase, credit loss from non-paying tenants will increase, eviction costs will increase, you'll have to offer concessions like free rent or temporary discounts to attract tenants and keep the property full. 

I pretty much set a 4 night minimum stay on days that are 20 nights out and a weekly discount for 7 days.

Once this happens buyers look at your property as damaged goods and any offers that come in will be discounted.

  :)  Ask other area investors which banks are good to work with.If you think you might buy most of that $6,000 in materials from one store, you might ask around at the stores in your area (Home Depot, Lowe's, possibly Menards) to see if they have some kind of volume discount or contractor program. 

You need to think 10X bigger (basically implying to discount the risk).I believe in calculated leverage.

I doubt anyone would discount their fee 50% to 150%.  

They have agreed to sell it at a discount and the ARV will be between 150k-200k above purchase price.

You're not at fault and your mortgage lender isn't going to offer you a discount so there's no obligation to discount the tenant.