Vkillers posted a list of hotels a month and a half ago which was very informative. I've reposted below and have added the Lien An to the list as I stayed there a few times. Am sure you can find even cheaper places in the backpacker district if your budget is really tight:
Lien An Saigon Hotel
Add: 37-39 -41 Le Anh Xuan Street, Ben Thanh Ward, District 1,
Ho Chi Minh City, Vietnam
Tel
84-8) 8272222
Home - LienAnSaiGonHotel.com
Room Rate: USD$32/USD$45/USD$60/USD$75/USD$95
Indochine Hotel
Add: 40-42, Hai Ba Trung st, Dist 1
Tel: 848-8220082 / 8220083
Room Rate: USD$30/USD$45/USD$60
Nam Phoung Hotel
Add: 46-48, Hai Ba Trung st. Dis 1
Tel: 848-8224446 / 8299766
Room rate: USD$45/USD$55/USD$60
N.Y Kim Phuong Hotel
Add: 22 Hai Ba Trung st, Dist 1
Tel: 848-8244290
Website: nykimphuonghotel.com
Room rate: USD$45/USD$55/USD$65
Thien Tung Hotel
Add: 70-74- Pho Duc Chinh st. Dist 1
Tel: 848-8213576 / 8212329
Room rate: USD$30/USD$40
Thai Binh 2 Hotel
Add: 04-06-08, Nguyen Hue A - TP. Long Xuyen-An Giang
Room rate: USD$30/USD$40/USD$50
An Trai Hotel
21B, Bui Thi Xuan, P. Ben Thanh Dist 1
Tel: 848-8325358
Room rate: USD$22/USD$27/USD$30
Son Trang Hotel
Add: 39, Bui Thi Xuan st Dist 1
Tel: 848-9253237 / 92532238
Room rate: USD$20/23/25/30
Lan Lan Hotel
Add: 42, Bui Thi Xuan, Ben Thanh Ward Dist 1
Tel: 9250159
Email:
[email protected]
Website: Login page
Room Rate: USD$18/USD$22/USD$25/USD$30
M2M Hotel
19B Bui Thi Xuan st, Dist 1
Tel: 9252676/9250242
Emal:
[email protected]
Room Rate: USD$25/USD$30/USD$45
Ngoc Ha Hotel
Add: 53-55 Le Anh Xuan st, Dist 1
website: ngochahotel.com
email:
[email protected]
Room rate: USD$30/USD$45/USD$65
Empress Hotel
Add: 136 Bui Thi Xuan, District 1, HCMC
Tel. +84 8 832 2888
Welcome to Empress Hotel
Cheers
Ice