AUsually you need the equivalent of 6 months of the rent up front before signing a lease contract. This consists of 2 months deposit, 2 months of key money, 1 month's rent in advance, and 1.05 month's agent fee. In addition, you need  to consider moving expenses. However, there are some properties for which don't require key money. So please check the conditions of the lease..

AIt’s possible but it really depends on the owner. There are some owners that might agree to no key money.The owner sometime change the conditions of the lease; no key money, reduce the rent and etc., when the apartment is vacant for a while.
Also the most of foreign companies are not agreed with key money, so we recommend to the owner that the monthly rent is adjusted to include the key money.
For example; Rent at 300,000yen which includes two months key money will be 325,000yen par month. (2 months key money =600,000yen ÷　24months (2years) ) This arrangement sometime works for the owner. Also we suggest to the owner that they should not require a renewal fee.

AAll personal lease contracts, plus some company lease contracts, require a guarantor.
Lessors(the owner) usually expect that a guarantor will be a relative who has enough income to guarantee that you will meet the financial obligations of the lease.
If you cannot find a suitable guarantor, you may use a ‘guarantor system’ which involves using a guarantor company.
The fee such guarantor companies require is usually 30 to 50% of the annual rent on the date of the contract and an additional 10,000yen per year for each year after the renewal.
Please check with your agent before signing a lease whether the owner will agree to you using a guarantor company.

AMost of the newer apartments have at least an air-conditioner, a hot water system and a gas cooking stove.
However, some newer apartments have additional appliances such as a dishwasher, a washer & dryer and a heated floor system. Also there is a usually a fiber optic line for internet and TV. You will see a full appliances in western style properties where a rent is over 500,000yen/ month. However if the apartment is older, there is sometimes no air-conditioner and no cooking stove. So you have to provide all the appliances by yourself in that case.
You can find a variety of inexpensive items at a home center or household appliance store.

Please check a floor plan or ask your agent.

AYou must provide an alien registration card. You can apply for this at the local ward office, even if you only have a temporary address in Japan.
Application;
Sample: http://www.moj.go.jp/ONLINE/ALIENREGISTRATION/17-1-1.html
You will need;
1.Your Passport
2.Two recent photos (within the last 6  months), 4.5cm×3.5cm showing the upper half of the body and no hat
Please note that you have to stay in Japan until you receive the alien registration card.
It takes about two weeks.
If you leave Japan during that time, it will be canceled.